Try resetting the play store app. You won't lose your apps following these steps. Nothing important will be lost.
Steps to follow on a motorola xoom
- Go to the app drawer (menu)
- Tap settings
- Tap applications
- Tap the "All" tab
- Scroll through and look for play store
- Tap Play Store (not play store services!)
- Tap "clear data"
- You will then get a warning, click "ok"
That's it, go through your problem again and see if it fixed. Bear in mind you will have to re-accept the terms and conditions for the play store app, when this comes up, simply click "accept"