When you had a leaked key / KMS activated before upgrade to Windows Media Center, Microsoft will know and block your activation by illegal activation step. But when you have your original license and still have these problems, it is really abnormal and maybe you will need to call MS... The most people that has been using the legit WMC promo key inside a KMS / leaked key activated system has these issues. It also is valid for the people having blocked product keys activated on their systems. Is a question of time to deactivate like that. Since now Microsoft can check for the activation health remotely, they also can deactivate your system even it is not connected to the internet (via log)...
We all good now. We back to activated! Smart move on my side by backing up my activation files... we'll see how long it lasts. Microsoft