I am running Firefox 14. I have reinstalled both Java and Firefox to no avail.
Go to Solution.
I decided to once more uninstall both Firefox and Java and reinstall. This time it worked. I believe that the previous attempts to install Java failed for some reason. Anyway, thanks for the help.
You can try to delete the Temporary Internet Files in the Windows OS Control Panel > Java. If the problem persists you may also have to contact the applet developer.
The problem is bigger than any one applet developer. Java is not working at all, no matter which applet I am using. I did try all your suggestions and Java still is not working.
Does Java work on the Java test pages?
Does the latest Java 6U33 still work on those websites?
See Java Platform > Java 6U33 (Download JRE)
Exactly same problem: ClassNotFoundException error - and no, reinstalling Firefox 14 and Java 7u5 did not resolve it.
In my case the solution was:
disable plugins.click_to_play in about:config.
I had enabled this (set it to true) to take advantage of FF14's clicl-to-play functionality - but apparently it stops Java from working properly!