my ipod wont sync to itunes through my computer

my ipod touch wont connect to my computer

everytime i try to connect my ipod to my computer it always comes up with a box saying itunes could not connect to this iphone. an unknown error occurred (0xE8000084)

its an ipod not iphone and i havnt jailbroken it so why is it saying this?

my brothers mac can connect to it

i've also got the latest update of itunes on my computer

please help me