There are a couple of current discussions on the site about this issue and there have been others since the iOS 5 update. That is of no help to you - but I just want you to know that you are not alone with this problem.
Did you try quitting Contacts on the iPad?
To quit the app.. Go to the home screen first by tapping the home button. Quit/close open apps by double tapping the home button and the task bar will appear with all of you recent/open apps displayed at the bottom. Tap and hold down on any app icon until it begins to wiggle. Tap the minus ➖ sign in the upper left corner to close the apps. Restart the iPad. Restart the iPad by holding down on the sleep button until the red slider appears and then slide to shut off. To power up hold the sleep button until the Apple logo appears and let go of the button.