Live Mail categories stop working / losing contacts?

Every few days, my Live Mail categories stop working. They show in the Contacts list, they contain email addresses, but trying to send mail to the category generates a message that I must include some contacts. I must then create a new category, copy the list of names to the new category, and delete the old one. Since I use these categories daily, this is a royal pain. It seems to occur when I am forced to reboot.  I have Live Essentials 2012, build 16.4.3505.0912, which I think is the most current.   Is there any way to stop this? Is there any work on fixing the problem?