pitivi crashed with UndoWrongStateError in checkpoint()

Pitivi crashed when I tried to render a video.
(I used a rotate effect in the video.)

ProblemType: Crash
DistroRelease: Ubuntu 12.04
Package: pitivi 0.15.1-0ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-23.36-generic 3.2.14
Uname: Linux 3.2.0-23-generic x86_64
NonfreeKernelModules: fglrx
ApportVersion: 2.0.1-0ubuntu2
Architecture: amd64
CrashCounter: 1
Date: Thu Apr 12 23:18:29 2012
EcryptfsInUse: Yes
ExecutablePath: /usr/bin/pitivi
InterpreterPath: /usr/bin/python2.7
PackageArchitecture: all
ProcCmdline: python /usr/bin/pitivi
PythonArgs: ['/usr/bin/pitivi']
SourcePackage: pitivi
Title: pitivi crashed with UndoWrongStateError in checkpoint()
UpgradeStatus: Upgraded to precise on 2012-04-03 (9 days ago)
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