After upgrading to TFS 2010 (from TFS 2005 or 2008) users may experience an intermittent problem where they are not able to see any projects in source control explorer, and/or getting one of the following errors:
TF14601 workspace doesn’t exist
TF14044: Access Denied: user D\U needs the AdminWordspaces global permission(s)
If your users see this issue, you can check for a recently discovered bug by running the following query against the TFS Configuration database:
SELECT * FROM tbl_security_identity_cache WHERE domain = 'Test' AND account_name = ‘foo’
Where "Test\foo" is the domain user name of any affected user. If the query returns multiple identity rows you are experiencing this bug. This will be the case if the original TFS 2005\2008 data contained more than one identity in Version Control with the same name (i.e. 'Test\foo').
Resolution: Contact Microsoft Customer Support Services for help cleaning up the accounts. You may be asked to provide a credit card number depending on the type of support contract you have, but ultimately the support case will be free because this is a problem in our product (we will revert any charges).