If I open a non-browser window and drag it so its x-coordinate is negative (i.e., off the left side of the screen), then when I restart Firefox and try to open that window again, nothing appears to happen. I can view the window in the Windows menu, but when I click it there, nothing happens. When I try to cycle to it with Cmd+`, nothing happens. I tested with the error console, view source, and page info windows. If I try the same with a browser window and hit Cmd+Q on the window that is partially offscreen, then on restart only the window that is offscreen appears; the original window, which was not offscreen, does not. I can view it in the Windows menu though. If I instead hit Cmd+Q on the original window and restart, both windows appear as expected. Part of the problem seems to be localstore.rdf. Offscreen windows have a negative "screenX" value, and it's these windows which I can't restore after restart. In the browser window case, only the browser that's focused when I hit Cmd+Q is saved to localstore.rdf. Problem is fixed after removing localstore.rdf and restarting. Problem appears in the July 16 nightly but not the 15th's: http://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/2010-07-16-03-mozilla-central/ Which are these changesets: http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=5fda39cd703c&tochange=96de199027d7 Which includes at least these window-related bugs: bug 574690 bug 575222 I'm away from my development machine, so I can't see if backing them out helps.

Possible dupes: bug 583316 bug 586605 bug 586578 bug 585410 bug 581840 bug 583560 bug 584249

The patch that caused this was backed out.