The problem is that you cannot delete a key and you cannot add the key as you do not have access to the key to delete it and the .NET framework cannot add it because of constraints on the StrongName data store.
The solution is to give yourself access to C:\Documents and Settings\AllUsers\ApplicationData\Microsoft\Crypto\RSA\MachineKeys\
- Browse to c:\Documents and Settings\AllUsers\ApplicationData\Microsoft\Crypto\RSA\MachineKeys
- Grant rights to Adminstrators, or whatever group you are in
- Take Ownership of this folder (click Advanced under Security, and then click the Ownership tab at the top)
This worked all fine for me see how you get along.