Well you most likely have a short circuit somewhere between Vcc and ground. It could be the USB serial converter chip, some cap, or maybe (the horror) more then one component short circuited. There comes a time when you have to decide if the time spent is worth the effort. If it is, then maybe use an ohm meter to read between Vcc and ground and if it shows a very low resistance, just start removing components one by one until the short circuit is removed. Me, I would write the board off as a learning experience and get a new one.Oh,I assumed it's a lost cause as soon as it went on the fritz and I did order a couple of replacement boards (at 11 bucks apiece with free shipping, no sense in wasting time wondering if I should or shouldn't replace it. The question was how many replacement boards should I grab (I settled for 4) .. With that about to be sorted in 2-3 weeks,I just want to experiment with the thing just for the challenge. In fact,aside from the tip about potential multi-component failure on the board(which I'll check out later this week),I found this useful little serial to ttl converter
and will see if that could be of some use reprogramming the 'unsalvageable' board. Worst case scenario - I'll waste a couple of hours honing my soldering skills and the best case scenario - I manage to reprogram the ATMega328 and use the device as intended.