I made a simple gear in SW2012 SP4 yesterday that used a couple equations to help size the gear and control it's tooth profile. I sent it to another person also using SW2012SP4 and he was unable to open the part. His instance of SW would hang and crash.

I checked the part this morning and it worked fine for me, so I resent the file to him, and that didn't help. I just checked about 1 hour ago and now the file doesn't work for me either. The file last modified date is still yesterday, so nothing should have changed.

How can I go about figuring out what is wrong with this? There are no debug messages appearing, and this "error" has me scared for other parts. The part in question is attached.