User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:32.0) Gecko/20100101 Firefox/32.0 (Beta/Release) Build ID: 20140602072051 Steps to reproduce: I have been noticing this since about a month ago. Intermittent STR: 1. Open a few tab. 2. Middle click on a tab to close it Actual results: The tab does not close until I do a right-click anywhere : inside the Nightly window or outside it. While the tab is in this semi-dead state, the "X" button on the tab does not get highlighted when i mouse over it. Expected results: tab should close when i do a middle click.

I may have stumbled upon a variant of this with Aurora 33: Firefox sometimes freezes for a few seconds when deleting a tab with mouse middle-click to the tab title. Tab does not disappear and also changing tab is impossible, Firefox is frozen. After a few seconds Firefox wakes and finally deletes the tab. But it also performs other mouse actions as if the deletion would have been done immediately: e.g. if I have re-clicked the tab trying to delete it again, Firefox actually also deletes the next tab (like it would have been on the place of the deleted tab when I made the second click). It almost sounds like Firefox pauses the screen updates, but performs the actions in background. This has happened a few times in the last 1-2 weeks, not very often, but every now and then. Mozilla/5.0 (Windows NT 6.1; WOW64; rv:33.0) Gecko/20100101 Firefox/33.0 ID:20140831004002 CSet: e9b04954e337 Windows 7 x64, Nvidia display card.

This is almost certainly a dupe of bug 1065463 . Since that bug is seeing more action, duping to it.