It seems so far that it only happens with the first tab when you first open the window. I'm wondering also if it's a linux only problem, because I have firefox on my windows 7 laptop and it has nothing wrong with it but on my laptop running Ubuntu 12.04 with all the latest updates and no add-ons it seems to happen all the time. At this point I expect it to happen but it shouldn't do this I know Mozilla didn't purposelly make the first tab broken. I wana know if Mozilla maybe in a few updates will ever fix it.
Do you mean that you can't close the first tab if you've opened extra tabs?
Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).
Do not click the Reset button on the Safe mode start window or otherwise make changes.