Important!!!!! Pleaze read I need your help!!!!

I'm having a major crisis and I need some advice.. I went out of town on business for a month and I came back happy just glad to be home. I decided to get on Diablo 2 expansion for the first time in a month.. I ws excited when i logged on.. I checked everything to make sure everything I have was still intact and it all was there. I log off and do a few things around the house and I try to relog on about a half hour later. I was absolutely floored when it said the horrible words.. "CD KEY IN USE BY ANOTHER APPLICATION" bla bla by some guy whos name I've never seen before The name is "onlyer"... I shudder when I think about someone stabbing me in the back by stealing my cd key from my Diablo 2 disk case that is on my desk in my game room. Also, I dont rule out the possibility of someone hacking into my computer and getting my cd key somehow. Anyway, bottom line is my cd key was stolen by somebody with the screen name "ONLYER" If is was somebody that came into my house in the month that I was gone, I will find out who did it and whoever it was will be sorry they ever stole from me!!!!!! If they were smart enough to get my account information from my computer and any of my items are gone then I will simply snap and hunt you down and whoop your sorry thieving ass!!!!!!Don't F with me!!! I hope whoever did reads this I would love to find out who did it... And, If it was someone that was in my house I WILL FIND OUT!!!!!!!!! Can anyone give me any advice on this matter Thanks

Jaymie In Dania, FL