I have an HP50G and I have changed new batteries three times in three weeks. Both set of batteries. It works fine from the USB cable. Not much into electronics, but I know how to open the 50G. I have already had it replaced by HP but they didnt collect the faulty one. SO I can experiment on this.
Any ideas?
Have you checked to see if your firmware is up to date?
If you carry around the 50g in a book bag, be careful it's not getting turned on in there by accident. (I put mine in a different case because of that issue)
Have the latest firmware. I bought 15 of the blue ones from Spain. And the first one I tried eats batteries. Luckily the others are fine. I even did what HP said and leave batteries off for two days and then inserted new ones... same thing, the batteries were dead and even though it was hardly used.