Steps to reproduce: 1. Open 3 or more tabs. 2. Double click on the close button of one of the last tab. Actual Result: 1. Tab is closed. 2. New Tab is opened Expected Result: 1. Tab is closed.

Does this happen in firefox's safemode? - http://kb.mozillazine.org/safe_mode If not, then I suspect it's one of your extensions causing problems.

WFM with Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv:1.9a1) Gecko/20060403 Firefox/1.6a1 which build are you using?

I experence the problem with all extensions disabled. I tested on the following builds Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8) Gecko/20060402 Firefox/2.0a1 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9a1) Gecko/20060403 Firefox/1.6a1

Duping forward, since Seth says he's going to fix it :) *** This bug has been marked as a duplicate of 343628 ***