Turning off hardware acceleration in FF fixed the issue for me:
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>,
Date: 03/12/2013 06:06 AM
Subject: Re: Fix Central and Firefox with the last update
Sent by: midrange-l-bounces@xxxxxxxxxxxx
True. Lately I am finding my FF 18.0.2 giving me fits. I have to exit
the browser and reboot often to clear it up. I copy a URL from IE to FF
and I get:
Your browser sent a request that this server could not understand.
Size of a request header field exceeds server limit.