Your crashreport:
https://crash-stats.mozilla.com/report/index/bp-0b901834-297f-4971-8db9-6ba992111104
Firefox 7.0.1 Crash Report [@ _purecall | nsXPTCStubBase::QueryInterface(nsID const&, void**) ]
This may be related to Trusteer Rapport. Try to disable it and see if that stops the crashing. For more help you can ask their helpdesk.
http://www.trusteer.com/support/en/report-problem

I stopped Trusteer and works fine. Thank you so much. But why did it just start having a problem. I have it for a while.

I have no idea why it starts crashing now. Maybe you can ask that to their helpdesk. According to the user in question 892517 Trusteer is aware of the problem and working on a fix.

Thank you again. I just leave as it is for a while.