Firefox 4.0b12 crashes all the time on 11.4

Firefox crashes each time I launch it under KDE.
It does not crash under IceWM.
Upstream Firefox binary does not crash, neither b13 nor RC1.
GTK-QT Theme Engine is reported missing by GTK settings.

Name : MozillaFirefox Relocations: (not relocatable)
Version : 4.0b12 Vendor: openSUSE
Release : 1.2.1 Build Date: nie, 27 lut 2011, 15:19:51
Install Date: nie, 13 mar 2011, 21:29:21 Build Host: build21
Group : Productivity/Networking/Web/Browsers Source RPM: MozillaFirefox-4.0b12-1.2.1.src.rpm
Size : 5073746 License: GPLv2+ ; LGPLv2.1+ ; MPLv1.1+
Signature : RSA/8, nie, 27 lut 2011, 15:22:46, Key ID b88b2fd43dbdc284
Packager : openSUSE:Submitting bug reports - openSUSE
URL : Home of the Mozilla Project
Summary : Mozilla Firefox Web Browser

Firefox starts under KDE as a new user though.

Killing ~/.kde4 allowed Firefox to start

It crashes with Gnome on 11.4, to be precisely, it stuck there on start-up, with its processes put in pipe_wait and wait statuses.
Maybe it’s related with libproxy, because it works well until I changed some proxy settings.

I have the same problem but with KDE…My crash “report details” are:
BuildID: 2011022200
CrashTime: 1300728617
EMCheckCompatibility: true
FramePoisonBase: 7ffffffff0dea000
FramePoisonSize: 4096
InstallTime: 1299777609
ProductName: Firefox
ReleaseChannel: default
SecondsSinceLastCrash: 223
StartupTime: 1300728615
Theme: classic/1.0
Throttleable: 1
Vendor: Mozilla
Version: 4.0b12

This report also contains technical information about the state of the application when it crashed.

4.0 Final just came out so expect to see it in repos in a few days, hopefully fixing some crashing issues.

It also crashes during bookmark management.

When I open the bookmark management window with the “open all bookmarks” option and go to “unsorted bookmarks”, it crashes the very moment I try to drag a bookmark into a folder.