There is something weird going on with applet heap memory.   This first came up in the following JAI forum thread:
  http://forums.java.net/jive/thread.jspa?threadID=23250&tstart=0

The reporter in that thread provided a simple applet and htm.  I modified it to display memory usage - see attached codes.   Also attached, Java console output from running this applet using JDK 1.6.0 b105 on the following environments:
 1) Windows XP (both IE and FF)
 2) Fedora Core6 Linux (32-bit, FF only)
 3) Solaris 10 (64-bit, FF only)

How to reproduce the issue
 o compile the code,
 o place the HTM and CLASS files together in a web server docs folder somewhere
 o ensure the Java Plugin has standard -Xmx64m setup, and that Java Console will open
 o open your browser (ensure Java Console is open) then navigate to the HTM file
 o once the applet finishes loading, press the browser refresh button
 o repeat the above step several times

What happens
 o when the appelt init()s it creates an array of bytes of size 55Mb
 o In the console, you'll see free/total heap memory used by the applet at each applet "lifecycle stage" (init, start, stop, destroy) as well as a list of applets in the applet context.
 o there is an OutOfMemoryError straight after the first time you try to refresh on all systems.
 
What is expected
 o the 55Mb array should be cleanly GC'ed after Applet/destroy() is called
 o no OutOfMemoryError
 o total heap memory shouldn't be increasing like that