Is Firefox infected

Last night I have seen that firefox is not working.
(it is not run at all)
Don't know the reason.but that night I installed some firefox addons.

As follows:
color zilla 1.0
fireshot 0.50
Gmail manager 0.5.5
Gmail space 0.5.94
Live http headers 0.14
show IP 0.8
User Agent switcher 0.6.11

But I don't think the situation occurred from addons but from any other source.

I never experienced such a situation ever before.
Is it a result of a infected virus or..?
I.E is worked well but not interesting to use it.
any one have solutions.?