I have let quite a few windows and tabs pile up (50 windows, 150 tabs!), after trying to download a file, firefox quit restarting (would crash upon opening, before any windows were drawn, whether the internet was connected or not, even if 'Cancel' was selected in the session dialog, or if i unchecked any number of windows. The log gave this: Crash ID: bp-6f9fd539-0979-490c-9bc2-11f672111012 I tried restarting the computer, starting firefox in safe mode (holding down the shift key while restarting firefox) all to no avail. The amount of time it takes for the firefox browser window to actually "collapse" does vary, from instantly to 10 or 15 seconds, being mostly almost instantly. Thanks for your time and help!