Had very recent issue (last few days) with 2 out of 120 users both firefox users but both also tried it on ie after firefox fouled up.
updating the Java to 7.11 cleared the problem in both cases. It would seem that firefox put several java versions in their blocklist pending a patch release to plug a vulnerability. Why it should also affect IE is a mystery - unless they did the same but didn't tell anyone.
Anyway - my problem resolved, users happy - worth a try
