From Bug report...4373190 there are two problems:
This is the second part which refers to the protocol etc.
The problem is I can't even move the check for updates window. The workout
is to minimize all other running applications and leave javaws the top one,
now the authentication window is over the updte window. This is annoying.

Further more, if you enter the username and password a little bit later,
 you can't lauch the application. (To reproduce, just wait for around 20 secs)

The following is the exception on solaris:
java.net.ProtocolException: Server redirected too many times (5)
        at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:552)
        at sun.net.www.protocol.http.HttpURLConnection.getHeaderField(HttpURLConnection.java:788)
        at java.net.URLConnection.getHeaderFieldInt(URLConnection.java:454)
        at java.net.URLConnection.getContentLength(URLConnection.java:366)
        at com.sun.javaws.cache.DownloadProtocol.doDownload(DownloadProtocol.java:546)
        at com.sun.javaws.cache.DownloadProtocol.getResource(DownloadProtocol.java:700)
        at com.sun.javaws.LaunchDownload.downloadJarFiles(LaunchDownload.java:498)
        at com.sun.javaws.LaunchDownload.downloadEagerorAll(LaunchDownload.java:404)
        at com.sun.javaws.Launcher.downloadResources(Launcher.java:539)
        at com.sun.javaws.Launcher.handleApplicationDesc(Launcher.java:221)
        at com.sun.javaws.Launcher.<init>(Launcher.java:119)
        at com.sun.javaws.Main.main(Main.java:129)

Sometimes ,the error is different:
Bad MIME type returned from server when accessing resource: ... .jnlp
text/html

I think that's the error message returned from web server.