Our Microsoft volume licensing site was recently updated to include our Windows 7 and Server 2008 R2 KMS keys. We have an existing KMS server running on Server 2008 (not R2). In an attempt to be proactive about supporting the new OSes in our environment, I unregistered the old KMS key with slmgr.vbs and tried registering the new key. The registration failed with Error 0xC004F050. The description for that error was "The Software Licensing Service reported that the product key is invalid."
What's wrong? I've checked and double checked that for typos against what is listed on the Volume Licensing website.