There is [https://support.mozilla.com/en-US/forums/contributors/707453?last=41751#post-41734 known] malware, a [http://www.microsoft.com/security/portal/Threat/Encyclopedia/Entry.aspx?Name=Trojan%3AWin32%2FSefnit.A particular trojan] that will crash Firefox 6. The same malware will affect earlier versions of firefox and other browsers but will not cause crashes. One possibility is that you have a malware problem, should that prove to be the case changing browsers may prevent crashes but result in greater security problems. It will be worth doing a full security scan of your computer, if you do that please state what software and version you used for any such scans. AFAIK MS often provides free security software capable of detecting this kind of problem. Firefox 6 works ok on my Windows machine, and possibly your problem is related more to your own setup than to Firefox itself. Have you looked at [[firefox crashes]] and [[is my Firefox problem a result of malware]]

Another common Fx 6.0 crasher lately has been due to Comcast's Constant Guard due to use of Idvault.