I've got a question...

Lately, when I want to close a window in Firefox, sometimes all of the windows end up closing. It's really, really aggravating, and I have no idea of why, or when, it will happen. A few days ago, for instance... At Moeboard, new windows open when you want to see the whole image, and I ended up right-clicking the windows closed instead of clicking the X on the window, because I'd have to re-open Firefox and go back to Moeboard four or five times. Otherwise, it seems to work fine... But, sometimes, it just happens, sometimes consistently. -_- Anyone know what could be up?