Wifi Sync to wrong computer

Preventing Sync

To prevent a specific computer from automatically synching with your iPhone or other idevice, go into iTunes preferences, devices, and check the box 'Prevent iPods. iPhones, and iPads from synching automatically'!

 

Kill.plist files

I had a similar issue where my MacPro somehow took over wifi sync of the iPad from the MacBook...

Fixed it by -

Quit out of iTunes on rouge computer, navigate to your user/Library/Preferences folder and look for com.apple.iPod.plist (and a lockfile if there) - delete (or rename if you need to feel warm fuzzy before deleting)
Restart iTunes - it won't have any iDevices now, you can re-add if you need

Then plug up with USB to the computer it should wifi sync to, and toggle the wifi sync settings off and on again, verify in the settings on the ipad