USB device not recognized

Hi i have an iPod Touch 4th gen and suddenly my pc stoped recognizing it. I though there was a software problem but it wasn't. I tried on 3 different machines (2 PC and 1 iMac) but still the same. Now i think this is hardware error and my question is does anybody knows how to fix that?or my ipod is dead. I am currently on itunes mode screen and is useless!

thank you in advance