it's not 100% of the time, but it's about 25.

Make sure that you do not click the close X on that tab.

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the add-ons is causing the problem (switch to the DEFAULT theme: Tools > Add-ons > Themes).

• Don't make any changes on the Safe mode start window.

See:

• Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

thanks for the reply, but that's not it.

the only add on i have is ad-blocker and i'm using the default theme.

I am experiencing the exact same behaviour with Firefox 3.6.13 on Kubuntu 10.10. Has anyone found out what is causing this issue? Anyone got a workaround? Quite an annoying "feature" :/.

How are you switching between tabs?

Does it also happen if you use Ctrl + Page Up or Ctrl + Page Down?

I'm just clicking on the tabs to switch between them. Will try and see what happens if I use Ctrl + Page Up / Down.

It's really annoying. Filling out a questionair, click over to another tab to look up some pertinant information, click back and - oh crap, it just closed! This has happened occasionally, maybe 10 percent of the time, for months, but this was the first time I really examined the problem. At first I thought that maybe I was accidentily clicking the little [X], but after clicking from one tab to another over and over again, I was able to repeat the problem, especially when clicking on the edge of the tab itself. It seems to happen more often when it's the last tabe or when it's loading. I will use ctrl + pgup/pgdn for now on as this appears to be a problem with the gui. I'm using 9.0.1 for Ubuntu cononical 1.0 and Unbuntu 11.10