linq to sql - [error] row not found or changed

I solved this error by redragging over a table from the server explorer to the designer and re-building. So indeed, the designer was out-of-synch with the actual SQL Table.

http://social.msdn.microsoft.com/forums/en-US/linqprojectgeneral/thread/c672c8ee-bf2a-41b4-bb8b-aa76cc5d9b95/