I'm using Firefox v22.0 on my Windows 7 machine. I've noticed that whenever I run Firefox and Skype at the same time, Firefox soon begins to slow down. A lot. To the point where it becomes unusable, yet technically has not completely frozen (barely). Even after I close Skype, it continues to happen, with the Task Manager showing Firefox's process using a consistent 50% of the CPU or higher. The only way to fix it is to close Firefox and reopen it.

If it helps, my Skype is version 6.3, and it may only happen if I use Skype's video chatting (it's the only reason I use Skype, so it's the only situation I've seen). It also doesn't happen immediately, only when Skype and Firefox are both open for a few minutes first.