I don't know if this counts or not but last year I was all set to go to Mercer (found housing, paid admissions deposit and accepted loans for first semester, had schedule in hand, etc.etc.) but had to decline shortly before classes began. I reapplied this year with no problems...
Of course this really wouldn't apply if you meant withdrawing after classes had already started. Is this something that you are dealing with right now? Could you share a little more info?