When testing NS6.1 Beta, after logged into sun.net, and clicked on Netfile(Java), some Java error showed on Java console (see stack attached below), and the action was aborted (Netfile page did not show), therefore could not access Netfile (Java). This was done on Solaris. When tried on Windows with the latest 1.4 (with some new fixes, as Stanley suggested), on Xiaobin's machine, could not logged into sun.net (that could be a local problem, but the Netfile (Java) problem was reproduced on all Solaris machine.
This bug is created based on 4409451 (maybe I should have reassign that one instead).
On the other hand, if switched 1.4 with 1.3.1, then it worked fine. Therefore, it seems some change in 1.4 caused the problem. Based on the error stack, the problem seemed to occur while java.util.zip trying to cache some file. The zip util seemed something new in 1.4, right?

Error stack from Java console (brief here, and full after brief):
Starting applet...
Opening https://central.sun.net/http%3A//centralapp3.central.sun.com/apps/main/n
etfile/rpUI.jar
Connecting https://central.sun.net/http%3A//centralapp3.central.sun.com/apps/mai
n/netfile/rpUI.jar with proxy=webcache-cup.eng:8080
Cookie Cache: false
Server https://central.sun.net/http%3A//centralapp3.central.sun.com/apps/main/ne
tfile/rpUI.jar requesting to set-cookie with "destinationURL=http://centralapp3.
central.sun.com:80/apps/main/netfile/rpUI.jar; domain=.sun.net; path=/"
Downloading https://central.sun.net/http%3A//centralapp3.central.sun.com/apps/ma
in/netfile/rpUI.jar to JAR cache
Cached JAR file name: rpUI.jar-5a4db866-1df2aedb
java.util.zip.ZipException: error in opening zip file
        at java.util.zip.ZipFile.open(Native Method)
        at java.util.zip.ZipFile.<init>(ZipFile.java:115)
        at java.util.jar.JarFile.<init>(JarFile.java:125)
        at java.util.jar.JarFile.<init>(JarFile.java:104)
        at sun.plugin.cache.JarCache$8.run(JarCache.java:1065)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.plugin.cache.JarCache.privileged(JarCache.java:361)
        at sun.plugin.cache.JarCache.access$1600(JarCache.java:64)
        at sun.plugin.cache.JarCache$CachedJarLoader.download(JarCache.java:966)

Full error stack:

Trace level set to 3: basic, net, security ... completed.
Loading certificates from JPI session certificate store
/home/joechou/.plugin140.log
Loaded certificates from JPI session certificate store
Added trace listener: sun.plugin.navig.motif.MotifAppletViewer[rp,0,0,1x2,invali
d,layout=java.awt.BorderLayout]
Added progress listener: sun.plugin.navig.motif.MotifAppletViewer[rp,0,0,1x2,inv
alid,layout=java.awt.BorderLayout]
Added trace listener: sun.plugin.navig.motif.MotifAppletViewer[rp,0,0,1x2,invali
d,layout=java.awt.BorderLayout]
Added progress listener: sun.plugin.navig.motif.MotifAppletViewer[rp,0,0,1x2,inv
alid,layout=java.awt.BorderLayout]
Loading applet...
Loading applet...
Initializing applet...
Initializing applet...
Starting applet...
Starting applet...
Opening https://central.sun.net/http%3A//centralapp3.central.sun.com/apps/main/n
etfile/rpUI.jar
Connecting https://central.sun.net/http%3A//centralapp3.central.sun.com/apps/mai
n/netfile/rpUI.jar with proxy=webcache-cup.eng:8080
Cookie Cache: false
Server https://central.sun.net/http%3A//centralapp3.central.sun.com/apps/main/ne
tfile/rpUI.jar requesting to set-cookie with "destinationURL=http://centralapp3.
central.sun.com:80/apps/main/netfile/rpUI.jar; domain=.sun.net; path=/"
Downloading https://central.sun.net/http%3A//centralapp3.central.sun.com/apps/ma
in/netfile/rpUI.jar to JAR cache
Cached JAR file name: rpUI.jar-5a4db866-1df2aedb
java.util.zip.ZipException: error in opening zip file
        at java.util.zip.ZipFile.open(Native Method)
        at java.util.zip.ZipFile.<init>(ZipFile.java:115)
        at java.util.jar.JarFile.<init>(JarFile.java:125)
        at java.util.jar.JarFile.<init>(JarFile.java:104)
        at sun.plugin.cache.JarCache$8.run(JarCache.java:1065)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.plugin.cache.JarCache.privileged(JarCache.java:361)
        at sun.plugin.cache.JarCache.access$1600(JarCache.java:64)
        at sun.plugin.cache.JarCache$CachedJarLoader.download(JarCache.java:966)
        at sun.plugin.cache.JarCache$CachedJarLoader.load(JarCache.java:734)
        at sun.plugin.cache.JarCache.get(JarCache.java:312)
        at sun.plugin.protocol.jdk12.jar.CachedJarURLConnection.connect(CachedJa
rURLConnection.java:81)
        at sun.plugin.protocol.jdk12.jar.CachedJarURLConnection.getJarFile(Cache
dJarURLConnection.java:63)
        at sun.misc.URLClassPath$JarLoader.getJarFile(URLClassPath.java:501)
        at sun.misc.URLClassPath$JarLoader.<init>(URLClassPath.java:462)
        at sun.misc.URLClassPath$2.run(URLClassPath.java:258)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.misc.URLClassPath.getLoader(URLClassPath.java:247)
        at sun.misc.URLClassPath.getLoader(URLClassPath.java:224)
        at sun.misc.URLClassPath.getResource(URLClassPath.java:137)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:193)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:189)
        at sun.applet.AppletClassLoader.findClass(AppletClassLoader.java:128)
        at sun.plugin.security.PluginClassLoader.findClass(PluginClassLoader.jav
a:172)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:304)
        at sun.applet.AppletClassLoader.loadClass(AppletClassLoader.java:108)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:260)
        at sun.applet.AppletClassLoader.loadCode(AppletClassLoader.java:373)
        at sun.applet.AppletPanel.createApplet(AppletPanel.java:542)
        at sun.plugin.AppletViewer.createApplet(AppletViewer.java:1232)
        at sun.applet.AppletPanel.runLoader(AppletPanel.java:478)
        at sun.applet.AppletPanel.run(AppletPanel.java:293)
        at sun.plugin.navig.motif.MotifAppletViewer.maf_run(MotifAppletViewer.ja
va:119)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.misc.URLClassPath.getLoader(URLClassPath.java:247)
        at sun.misc.URLClassPath.getLoader(URLClassPath.java:224)
        at sun.misc.URLClassPath.getResource(URLClassPath.java:137)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:193)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:189)
        at sun.applet.AppletClassLoader.findClass(AppletClassLoader.java:128)
        at sun.plugin.security.PluginClassLoader.findClass(PluginClassLoader.java:172)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:304)
        at sun.applet.AppletClassLoader.loadClass(AppletClassLoader.java:108)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:260)
        at sun.applet.AppletClassLoader.loadCode(AppletClassLoader.java:373)
        at sun.applet.AppletPanel.createApplet(AppletPanel.java:542)
        at sun.plugin.AppletViewer.createApplet(AppletViewer.java:1232)
        at sun.applet.AppletPanel.runLoader(AppletPanel.java:478)
        at sun.applet.AppletPanel.run(AppletPanel.java:293)
        at sun.plugin.navig.motif.MotifAppletViewer.maf_run(MotifAppletViewer.java:119)
        at sun.plugin.navig.motif.MotifAppletViewer.run(MotifAppletViewer.java:115)
        at java.lang.Thread.run(Thread.java:579)
WARNING: Unable to cache https://central.sun.net/http%3A//centralapp3.central.sun.com/apps/main/netfile/rpUI.
jar
Opening https://central.sun.net/http%3A//centralapp3.central.sun.com/apps/main/netfile/rpUI.jar
Connecting https://central.sun.net/http%3A//centralapp3.central.sun.com/apps/main/netfile/rpUI.jar with proxy
=webcache-cup.eng:8080
Server https://central.sun.net/http%3A//centralapp3.central.sun.com/apps/main/netfile/rpUI.jar requesting to
set-cookie with "destinationURL=http://centralapp3.central.sun.com:80/apps/main/netfile/rpUI.jar; domain=.sun
.net; path=/"
Opening https://central.sun.net/http%3A//centralapp3.central.sun.com/apps/main/netfile/rpUI.jar
Connecting https://central.sun.net/http%3A//centralapp3.central.sun.com/apps/main/netfile/rpUI.jar with proxy
=webcache-cup.eng:8080
Server https://central.sun.net/http%3A//centralapp3.central.sun.com/apps/main/netfile/rpUI.jar requesting to
set-cookie with "destinationURL=http://centralapp3.central.sun.com:80/apps/main/netfile/rpUI.jar; domain=.sun
.net; path=/"
Downloading https://central.sun.net/http%3A//centralapp3.central.sun.com/apps/main/netfile/rpUI.jar to JAR ca
che
Cached JAR file name: rpUI.jar-5a4db866-6c5ed91d
java.util.zip.ZipException: error in opening zip file
        at java.util.zip.ZipFile.open(Native Method)
        at java.util.zip.ZipFile.<init>(ZipFile.java:115)
        at java.util.jar.JarFile.<init>(JarFile.java:125)
        at java.util.jar.JarFile.<init>(JarFile.java:104)
        at sun.plugin.cache.JarCache$8.run(JarCache.java:1065)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.plugin.cache.JarCache.privileged(JarCache.java:361)
        at sun.plugin.cache.JarCache.access$1600(JarCache.java:64)
        at sun.plugin.cache.JarCache$CachedJarLoader.download(JarCache.java:966)
        at sun.plugin.cache.JarCache$CachedJarLoader.load(JarCache.java:734)
        at sun.plugin.cache.JarCache.get(JarCache.java:312)
        at sun.plugin.protocol.jdk12.jar.CachedJarURLConnection.connect(CachedJarURLConnection.java:81)
        at sun.plugin.protocol.jdk12.jar.CachedJarURLConnection.getJarFile(CachedJarURLConnection.java:63)
        at sun.misc.URLClassPath$JarLoader.getJarFile(URLClassPath.java:501)
        at sun.misc.URLClassPath$JarLoader.<init>(URLClassPath.java:462)
        at sun.misc.URLClassPath$2.run(URLClassPath.java:258)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.misc.URLClassPath.getLoader(URLClassPath.java:247)
        at sun.misc.URLClassPath.getLoader(URLClassPath.java:224)
        at sun.misc.URLClassPath.getResource(URLClassPath.java:137)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:193)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:189)