We have identified one solution for the instability problems with Firefox on Windows. The F-Secure Browsing Protection toolbar is causing Firefox crashing for users of e.g. FarmVille, a lot of other Facebook games, and HeiaHeia.
A quick solution for the problem is to switch off the F-Secure plug-in from the browser, but please make sure that your virus protection is up-to-date also after doing that. For any issues with product security, please consult F-Secure support or e.g. your system administrator. More info on the problem at the Mozilla Firefox support forum: http://support.mozilla.com/en-US/forum/1/651329?s=litmus_ff&as=q
This might not be the only source of instability in the Firefox browser, so please let us know, if it doesn’t help.
Our apologies regarding any frustrations and thanks for your patience with this issue!