Has anybody experienced this? In the last couple of days I've noticed that when I try to close a Firefox tab it won't. I've had to close then reopen Firefox to be able to close the tab. Couldn't find a fix for it anywhere. It's damn irritating!
If this is happening consistently every time you use Firefox, try opening FF in safe mode. Use the shortcut in the programs menu. If it does not reoccur, then chances are either an extension is causing problems or something is corrupted in your profile.