Your crashreport:
https://crash-stats.mozilla.com/report/index/bp-ccbbb471-e3c4-43c4-87b1-f83dd2111105
Firefox 7.0.1 Crash Report [@ _purecall | nsXPTCStubBase::QueryInterface(nsID const&, void**) ]
This is caused by Trusteer Rapport. Try to disable it and see if that stops the crashing.
You can stop Rapport using Start Menu > Programs > Trusteer Rapport > Stop Rapport
You can ask their helpdesk when an updated version of their product will be made available or, if you don't need this software, uninstall it.
http://www.trusteer.com/support/en/report-problem
According to the user in question 892517 Trusteer is aware of the problem and working on a fix.
See also Bug 699776 - crash in nsXPTCStubBase::QueryInterface involving RapportTanzan7.dll in the stack.

Thanks for the feedback. I have literally just installed release-candidate v8.0 and this (so far) is loading OK. However, I will bear in mind the possible need to disable Rapport (used by the interface with On-Line Bank that I use).

Thanks again.

I had this too and stopping rapport sorted the problem. I'm going to look into setting the rapport service to manual and then just starting it when I need to do online banking. (I'm using Firefox 3.6 - yes, I know but the software I work with requries it - and Windows XP Pro)