I've got an assembly file that hangs when opening. The problem seems to be related to a few parts that have a sketch with an external block in the sketch. If I rename the blocks the assembly opens - no problem. If the block is not renamed SolidWorks hangs, if I click anywhere on the screen SolidWorks crashes instantly no error message, nothing, just poof it's gone. I can open the individual part files with the block just not the assembly.

I'm running SolidWorks 2010 x64 SP4.0

Any ideas?