Not long after installing WLM 2011 aka WLM 15, I noticed it crashed very regularly. A bit of Googling brought up AVG as the culprit, whereas I have Microsoft Security Essentials installed.
I added the Windows Live directory to the exceptions anyway and wouldn't you know - WLM 2011 is now rock solid.
Here's the screen for you MSE users -
Set yourself a reminder to remove the exception after a month or the next Live Essentials update when the problem is hopefully fixed.