I am using Ubuntu 9.10 (Karmic Koala) and my Java stopped working on Firefox as soon as I upgraded it to 3.6.

After searching for a while, it seems like the JRE must be upgraded to 1.6.0.18. Okay, upgraded the JRE and the Java started working ! yay... the applet area appeared on the rendered page and I wait a while to the page to be fully loaded. Then I expected the applet will start, but... wait... my Firefox status bar already showed "Done" but nothing happened to the applet area. It is still blank with grey background.

I patiently waited a while.... no, nothing changed. Something is wrong. I started googling and found out some people complaining about Java not working with Firefox 3.6. Really ?!

After several days (!!) searching for a solution I landed to this page:

http://java.sun.com/j2se/1.5.0/docs/gui ... /xawt.html

Well, I don't know why it must be this hard to find this guide, but seems like this must be the solution I am looking for.

Decided to add an environment variable "AWT_TOOLKIT", I opened up my .profile just to find out that it is already there !

export AWT_TOOLKIT=MToolkit

is already in my .profile. Hmm... I could not recall when I added it. At all. But it is there and I must have added it in order to solve the similar problem before, which turned out to be ineffective this time.

Then I tried the other option:

export AWT_TOOLKIT=XToolkit

Restarted Firefox (You need to make sure the new value is being used. If you really are not sure, just logoff and login back again) and this time the Java really worked !!

So the culprit is the wrong value in the environment variable ? How about if I delete it ? Out of my curiosity, I removed the export line from my .profile and restarted Firefox again. It is still working!

Well, well... I turned out that the fix in the past was the source of the present problem.