I have an Asian friend who is a British citizen card valid until early next year. He got a Schengen visa last October from the Maltese Embassy. 15 days until April 2013. We did not know at the time what has happened now.
He has used 13 days and booked several trips to France and Spain in the following weeks, so we thought he could go to the French embassy to sort it out. The French embassy said that because he already had a Schengen visa from Malta, they could not do anything and that he should go sort it out with the Maltese Embassy.
The Maltese Embassy have however refused to extend or cancel the visa saying they cannot cancel/revoke as the visa has already been used and that they cannot extend an existing visa until it expires! So there is no way out??