The combo box at the following link doesn't work with 1.6.0-rc-b61 build.
http://java.sun.com/docs/books/tutorial/sound/SoundApplet.html
The drop-down box wasn't opened when the field was clicked. And here is the message from the java console box.

Java Plug-in 1.6.0-rc
Using JRE version 1.6.0-rc Java HotSpot(TM) Client VM
User home directory = C:\Documents and Settings\dtftest
network: Loading user-defined proxy configuration ...
network: Done.
network: Loading proxy configuration from Internet Explorer ...
network: Done.
network: Loading manual proxy configuration ...
network: Convert proxy bypass list to regular expression:
network: scaweb1.sfbay.sun.com:8080 --> SCAWEB1.SFBAY.SUN.COM:8080
network: Done.
network: Proxy Configuration: Manual Configuration
     Proxy: http=scaweb1.sfbay.sun.com:8080,https=scaweb1.sfbay.sun.com:8080,ftp=scaweb1.sfbay.sun.com:8080
     Proxy Overrides: scaweb1.sfbay.sun.com:8080


----------------------------------------------------
c: clear console window
f: finalize objects on finalization queue
g: garbage collect
h: display this help message
l: dump classloader list
m: print memory usage
o: trigger logging
p: reload proxy configuration
q: hide console
r: reload policy configuration
s: dump system and deployment properties
t: dump thread list
v: dump thread stack
x: clear classloader cache
0-5: set trace level to <n>
----------------------------------------------------

basic: Registered modality listener
basic: Referencing classloader: sun.plugin.ClassLoaderInfo@133796, refcount=1
basic: Added progress listener: sun.plugin.util.GrayBoxPainter@1632c2d
basic: Loading applet ...
basic: Initializing applet ...
basic: Starting applet ...
network: Connecting http://java.sun.com/docs/books/tutorial/sound/example-1dot2/playing.jar with proxy=HTTP @ scaweb1.sfbay.sun.com/129.145.155.90:8080
network: Connecting http://java.sun.com/docs/books/tutorial/sound/example-1dot2/playing.jar with cookie "SUN_ID=192.18.42.11:295041124920259; s_cc=true; s_sq"
network: Downloading resource: http://java.sun.com/docs/books/tutorial/sound/example-1dot2/playing.jar
Content-Length: 558,131
Content-Encoding: null
basic: Loaded audio clip: http://java.sun.com/docs/books/tutorial/sound/example-1dot2/spacemusic.au
basic: Loaded audio clip:

http://java.sun.com/docs/books/tutorial/sound/example-1dot2/bottle-open.wav
basic: Loaded audio clip: http://java.sun.com/docs/books/tutorial/sound/example-1dot2/jungle.rmf
basic: Loaded audio clip: http://java.sun.com/docs/books/tutorial/sound/example-1dot2/flute+hrn+mrmba.aif
basic: Loaded audio clip: http://java.sun.com/docs/books/tutorial/sound/example-1dot2/trippygaia1.mid
Exception in thread "Thread-10" java.lang.NullPointerException
at java.util.Hashtable.put(Unknown Source)
at AppletSoundList.putClip(AppletSoundList.java:27)
at AppletSoundLoader.run(AppletSoundLoader.java:25)