I've noticed that Jd2 deducts traffic from premium accounts when downloads start, and then again when they finish. If you're getting near the end of your download limit, that can result in "no traffic available" or some such message when you could have a lot of traffic left. Then you have to trick it into allowing you to download the remaining amount (I won't go into how).

It'd be nice if it only deducted at the start, or at least didn't deduct traffic again when finished.