Your advice here is not going to get better than that offered to you in Bugzilla. https://bugzilla.mozilla.org/show_bug.cgi?id=1534065 "I already tried starting it in safe mode. I checked "Disable addons" but pressing button "Make Changes and Restart" has no effect. Thunderbird starts fine with clean profile though" I suggest you try the continue option. You have not tried safe mode unless you have tried to actually use the application in that state. My feeling is you have issues with your graphics driver and a new profile turns off the hardware acceleration, just as safe mode does (If you actually run in that mode)