vermillion 52 x86 installed on snv_51
Problem does not occur on sparc.

Open a java applet in a browser (attached sample applet)
It appears that the applet attempts to execute but fails.
(/usr/java/bin/appletviewer displays the applet correctly
other testcase
browse to
http://www.jeacle.ie/mortgage/

prstat -a shows
firfox-bin at 38%
Xorg at 36%
java_vm at 22%

firefox is effectively hung - it will not respond to user
there is no problem displaying this page on sparc systems.
As this bug is causing the browser to hang I'm marking it a stopper.
I am experiencing something similar, where my machine goes to 100% CPU when I try to run an applet. This is also a show-stopper for me.
One more comment for your information: this also happens to me on build 49. It did not occur previously; it seems to have started happening when I did a live upgrade to build 53.