I would first wonder about Securom. You didn't mention in your post if you were Securom-free, only that you are currently using a no-crack CD.
You did mention deleting the cache file and getting back in again, but you didn't mention if you had logged out and back in again with a fresh restart on your computer while looking for the annoyance/problem. So I might wonder if all the entering and exiting of the game might have been an issue.
So far as I am aware, I am SecureRom-free. I rebuilt the system from a completely blank hard drive a couple of months ago, and have never since then started the game without the No-CD crack in place. I have not installed other games, either, so there has been no source for SecureRom to be installed or activated on my system.
As for rebooting, yes, I had rebooted completely a few times, before thinking of deleting the groups.cache, and the reboots (full power-off/power-on reboot) had not helped.
As I said, I appreciate the ideas and thoughts. :-) Thank you very much! If (when?!) it happens again, I will remember the groups.cache and see if that *is* the culprit. :-D