HowardW (6/10/2013)
Start SQL Server in minimal configuration mode from the command line (-f flag). This will create tempdb in the default location and allow you to run an ALTER command.
This worked for me.
scripted my planned change
opened a New Query in mgt studio, propted me for the UID and Pwd.
Ran my script.
removed my switches and restarted the server.
Problem solved. it took me longer to find this solution than to apply a working fix.
-side note
I have no idea what caused the issue in the first place.