User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:34.0) Gecko/20100101 Firefox/34.0 Build ID: 20141120192249 Steps to reproduce: See: http://forums.mozillazine.org/viewtopic.php?f=9&t=2880521 It's not a 100% reproducible problem but basically, if you have OMTC on, Firefox will freeze *sometimes* when switching tabs, with flash or not. I highly doubt it should has been reported here but I can't find. So feel free to mark as dupe.

Shouldn't this block OMTC? Because the bug got introduced with OMTC and goes away when disabling it, so it probably should be a fault in OMTC?

Benjamin, does bug 1067470 or any if its duplicates sound familiar? Or is Firefox actually hanging in your case? You can test this by trying to open a new tab with CTRL + T when the bug strikes.

(In reply to Johan C from comment #3) > Benjamin, does bug 1067470 or any if its duplicates sound familiar? > > Or is Firefox actually hanging in your case? You can test this by trying to > open a new tab with CTRL + T when the bug strikes. I really didn't ever try switching to other applications. I will do it next time I encounter hanging problem.

This bug looks like duplicate of bug #1067470, so I'm marking this as one.