unity-2d-spread crashed with SIGABRT in g_option_context_parse()

[Wizard]

Qt theme was changed with qtconfig from "Windows" to "GTK+". Unity's "tile launcher" disappeared (crashed).

ProblemType: Crash
DistroRelease: Ubuntu 12.04
Package: unity-2d-spread 5.8.0-0ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-22.35-generic 3.2.14
Uname: Linux 3.2.0-22-generic i686
ApportVersion: 2.0-0ubuntu4
Architecture: i386
Date: Sat Apr 7 17:57:14 2012
ExecutablePath: /usr/bin/unity-2d-spread
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release i386 (20111012)
ProcCmdline: /usr/bin/unity-2d-spread
ProcEnviron:
 SHELL=/bin/bash
 PATH=(custom, no user)
 LANG=pl_PL.UTF-8
Signal: 6
SourcePackage: unity-2d
Title: unity-2d-spread crashed with SIGABRT in g_option_context_parse()
UpgradeStatus: Upgraded to precise on 2012-04-07 (0 days ago)
UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare

[Apport retracing service (apport)]

StacktraceTop:
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[Albert Astals Cid (aacid)]

Seems to be aborting because of "GTK+ 2.x symbols detected. Using GTK+ 2.x and GTK+ 3 in the same process is not supported" (or so says the stacktrace)