My ipad never finish the update.

ipad software version 3.2

itunes version 10.5.1.42

I have left if connected days and never finish the update. Today is 2 days connected trying to sync and still on Backing up on Step 1 of 4.

Do I have to get any other download?

What do I have to do?

I have done the process in my iphone without problems, but need help with the ipad!!!