Created attachment 445010 [details] emerge --info Error on terminal: [2640] ###!!! ABORT: X_CopyArea: BadDrawable (invalid Pixmap or Window parameter); 3 requests ago: file /var/tmp/portage/www-client/seamonkey-2.42.3.0_p0/work/thunderbird-45.3.0/mozilla/toolkit/xre/nsX11ErrorHandler.cpp, line 157 It seems related to Bug 563752.
Could you try rebuilding it with USE="-system-cairo" and see if it still crashes?
(In reply to Ian Stakenvicius from comment #1) > Could you try rebuilding it with USE="-system-cairo" and see if it still > crashes? That did the trick! Though it would be nice to solve the issue with system libs... (BTW, other crashes still happen: no console message, possibly again Bug 562930.) Let me know if further action is needed on my side.
Unfortunately, system-cairo is a lost cause -- upstream is using a heavily patched fork based on cairo-1.9 while current upstream is somewhere around cairo-1.14, things have simply diverged too much. However, the flag should be masked the same as other mozilla products so I'll do that now. Thanks for reporting!