I am currently running Firefox 3.6.23 (hate the latest version reason I am have not updated to latest version) and I just reinstalled my system few months back. I went to play a game today and it said I was missing the Java applet for the game so I clicked find applet and firefox did a look for it and it failed to install so it gave me a manual install button.
I then clicked that and it took me out to the official Java website with the file that FF had failed to download and I went ahead and manually downloaded and installed the java applet program.
I then went back to the game site and when I ran the game it crashed firefox.
I know I have a chat site I use to frequent and same thing when I tried this few weeks back when I went it said it was missing and tried to install it and it would crash the browser even though in the past it worked fine.
What might be causing firefox to crash when running a java applet even though the program fire fox suggested is installed properly.
I'm a little concerned that in your "More system details" list you appear to have two different Java plugins:
Next Generation Java Plug-in 10.5.1 for Mozilla browsers
Classic Java Plug-in 10.5.0 for Netscape and Mozilla
Could you disable the older one and test again?
Tools > Add-ons > Plugins
Also, please be advised that numerous security vulnerabilities have been publicly disclosed in version 3.6.23, so at some point, you really should update. I'm not sure what you "hate" about Firefox 14, but since the UI is very customizable, most things that people dislike can be fixed in a few minutes.
As for the reason it's the header part of the browser as I have found it in fact to be not that customizable as I tried moving these to where I wanted and seems it would not allow it to be moved where I wished it to be!!
As for the java. I tried disabling the older one and no good same results and then I tried swapping the disable around disabling the newer one leaving the older working and it pops up saying I am missing the plug in for the feature and to please download it.