Gdetrailer is dead on re security. Anything microsoft will report your every move back to Central for future sales. And they are far from the only big offender.
I run every anonymizer i can think of, clear all data after a login (like to here) when i leave the site, and switch VPN IPs regularly. I'm not trying to beat the NSA, just the sleazebags that want to sell my privacy.
As to OP, I'm not seeing any problem with FF (latest version whatever that is) and agree with shut down and restart as a first option. Could it be competing browsers if you have them open at the same time?