Ah, I've read the club site now. I remember Paul Barber saying the paperwork for both players had been completed from our side, and the article I linked did say Charlton were going to appeal.
Brighton cancelling his contract is another way of doing but it is very poor of the FA to mess them...
As I understand it, Charlton faxed the papers to the FA at 16.59 (the window closed at 17.00) whereas the FA said they'd been sent after the window closed. Charlton disputed it, and it seems they've won...