Here's the process: Open a page. Right-click a link and open the link in new tab. La la la, browse along, open as many tabs as you like. Right-click a tab for a page that you're not viewing currently (non-active tab). Click "Close tab". Note that you just get the wacky Aqua-background display (white/off-white lined window) with a single "aqua bar" at the top. See screenshot. Nothin you do to this window will get you back to a usable state. You have to use a different window. You've lost all your tabs. Mozilla 1.2 Beta Mac OS X. Happened on three different machines. Doesn't ALWAYS happen -- don't have time to test the conditions right now. I know it never happens if you have "load tabs in background" turned on and you never switch away from your initial tab. You have to switch around a bit, then close a tab that you're not viewing. Do this enough, and it'll happen....or I am 100% insane. See the screenshots (before and after).

before the closing

After the closing

I'm able to reproduce this 100% on 2002102208, Mac OS X 10.1.5, by doing: - open a new window with a page with several links (at least three) - open three links from this page in new tabs (this is with "Load links in the background" enabled) so you now have four tabs - select the third tab - Ctrl-click the second tab and select "Close Tab"; you should be looking at what is now the second tab, but will see the content of the third tab - Ctrl-click what is now the third tab, and close it; you should now see the striped background At this point, it can be recovered by going back to the first tab, then to the second. If, however, you close the confused tab, the window becomes difficult to use.

*** This bug has been marked as a duplicate of 173703 ***