When doing an upgrade in place from VS2008 to VS2010, the builds fail even after configuring workspaces related to "Workspace Mappings already exist under servername_XX"
So this is an easy fix with the Workspace Sidekick by removing all mappings the build service still has. However, Attrice hadn't released Sidekicks for VS2010 RC1 as of yet.
Powershell console doesn't install as a part of the Team Foundation Sidekicks for RC1. Tried installing the Sidekicks 3.0 for Beta 2 and it didn't work. Tried running tf commands from Sidekicks 2.4 to remove workspaces from command prompt. That command wasn't recognized.
Finally the workaround was to go to a workgroup server where we were testing Beta 2 which had Team Foundation Sidekicks 2.4 installed on it. It took all of 30 seconds to remove the workspace mappings and get a clean build.
But had two days downtown of no builds because of this issue.