hmmmm...I wasn't aware of that one with SCtrade. I'm guessing the money that was transferred is the proceeds from a stock sale and the three day wait is because of the 3 day settlement rule. If that's the case, if you had a margin account they wouldn't put a hold on the money. Even though you're not buying the stock on margin per se, if you're trading from a margin account the funds are available immediately. I do it all the time.
Maybe if you signed the margin agreement paperwork they would make the funds available for you. You can download the form from their web site, it's really just a signature agreement, the form is filled out, and then fax it to your branch.