That on regular Windows or VMWare Biffa?
Only on regular windows. Linux seems fine.
Just been checking a abit and it seems there might be some bad WU's around in the 6900 batch.
Mine was: Project: 6900 (Run 32, Clone 24, Gen 41)
Confirmed bad WU: http://foldingforum.org/viewtopic.php?f=19&t=18522&p=185211#p185211