Premiere CS6 Crashing when creating a multitrack sequence

Every time I try to create a sequence with multiple mono tracks, Premiere crashes with the following message:

Error in:

/Volumes/BuildDisk/builds/slightlybuilt/shared/adobe/MediaCore/Backend /Make/Mac/../../Src/Component/AudioPanProcessor.cpp-214

And freezes. 

I'm on a MacPro with 24GB RAM, OS10.7.5
Worked fine yesterday, and now fails even when loading previous projects with multitrack sequences.

I'd be grateful for any ideas.