Today I've encountered a strange error when opening the Source Control Explorer: Team Foundation Error Method not found: 'Boolean Microsoft.TeamFoundation.VersionControl.Client.Workspace.OwnerNameMatches(System.String)'. That denied any use of the source control. I’ve tried re-applying Visual Studio 2010 SP1 and TFS 2010 SP1 but to no avail. Eventually, only after a complete uninstallation and reinstallation of Visual Studio 2010 SP1 the error has gone. Hmmpf.