error 3194 when trying to update to ios 5.1.1

i can not update my iphone 4, when i try to update on i tunes it extracts the software but when it gets to verifying iphone i get the error code 3194,

i have tried to update also on the phone through the iphone and get a message saying not enough free space you need at least igb of free space.

i have also tried turning of norton security and firewall but no joy.