I'm trying to cancel some reservations for a few days now and every time I get a message saying there was an error and to try again. It then signs me out and when I sign back in, it can't find my reservations.
I can honestly say that I haven't had problems like that because I don't book using the online system ... I like the personal interaction a little more!
Anyway, if you continue having trouble canceling something just give the good old main line a buzz and speak with a Cast Member. 1-407-W-DISNEY