Information Rights Management Problems

I have successfully been using the Microsoft IRM to protect some important Excel files since 2006. Everything was hunky dory until 18th November, when suddenly I was no longer able to open the file. I received the follwoing message "You do not have credentials that allow you to open this workbook. You can request updated permission from....", the from being myself!

The original file was on a laptop running XP with all the latest updates. Other protected files also no longer worked. I tried the file on a pc running Vista with the same result. The problem appears to be with the IRM licensing server, and lookin at other forums, I am not alone. Is there anyone here aware of the problem, or know whether Microsoft are investigating it.

I have tried creating a new file and protecting that with IRM, and it works. Microsoft have succeeded in locking me out of my own files!