iPod touch My iPod touch g3 has trouble charging and the comp seems to think its an iPhone

I hope someone can help I'm new to the iPod. And have recently brought a second hand iPod touch 3rd generation, we only got USB charger with it. Whenever I plug it in it struggles to charge I often get the message saying that charging isn't supported on this accessory. I have also had an error message spear on my iTunes which says ITunes cannot connect to this iPhone An unknown error has occurred (0xE8000084) it's really frustrating as obviously its not an iphone. I have tried my partners charger as she got one from the same person but my ipod says the same. Her ipod was charging fine but has now started doing the same also hers doesnt hold a charge, so please any advice would be appreciated.