Bloody frustrating is what is.
You're not the first and likely not the last but David Barker (author of MCS) claims he's never seen it and can't reproduce it so he can't do anything about it.

I've brought it up more than once but have yet to nail down a repeatable procedure to repeat it - it feels completely random. I can code for hours without it crashing, then the next day it crashes 5 times in an hour and it's impossible to put the finger on what is that triggers the crash. There are threads here and over at Melabs....

Please do tell Melabs and/or Mechanique, if more people reports problems maby, just maby they'll actually look into it. So, if anyone else experiences this please do post.

/Henrik.