When invoking TFPT you might get one of the errors:
Unable to determine the workspace
Unable to determine the source control server
To get around this try invoking tfpt from within a directory that is already mapped to Team Foundation source control.
If that doens't do it your local workspace cache may need to be updated. This can done via, tf workspaces /s:<server URL>
Thanks to on of the TFS Developers, Ben Ryan, for this pointer!