My Ipod will not reboot using Itunes. Says device not found and my serial number not matched to my unit. Tried all day and no support or luck.

My Ipod will not reboot using the tools on Itunes. My messages are that my serial number doesn't match my unit and a error code (28) pops up. The unit, when installing the new software, shows the Apple icon and down load bar but it disappears and the error messages re-appear. No luck from Apple on verbal tech assistance via phone... I just down loaded Itunes today so I have the latest version. I also completely updated my computer with 61 new up dates and checked my firewall...all in good working order.