WTF?!?

Today I've been having trouble with my web browser.

I usually have 2-3 windows open at the same time. I may be streaming a video off of Youtube and reading a news article or something else to pass the time while the movie loads. When I go up to the little red X and click it to close the window every window I have open closes.

This is pissing me off and i've done several virus scans and nothing's come up, how do I fix this shit?

Rebuild time.

*bump* for an actual answer thats actually helpful

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Not too good at taking the advice given are you? NO EXCEPTIONS! Rebuild motherfucker, time to use it.

Win/Mac/Linux?  Firefox, we presume?  What the F--- are you running?  Can't help w/o info.