Any robots.txt revisions applied inside VS2010 save the file with BOM which basically causes Google to reject it with a 'Syntax not understood' error. There is a related question on this but the "Save With Encoding" option isn't available for text files - even if it were, there should be a solution that just works with CTRL + S rather than having to go the advanced route just to keep BOM out.
I can't believe I'm the the only person experiencing this problem, surely there's a solution?
Looks like an easy fix for this is to have a blank line or a comment as the first line of the file: http://www.12titans.net/p/robots-txt-bom.aspx