1. Try going
Settings>Accounts>Google>Tap your
account> tap three dots in the upper
right (or press menu button) "Remove
Account".
2. Go to "Settings"->Applications-
>Manage Applications
3. Select "All"
4. Scroll to and tap Google Play Store
5. Tap Force Stop, tap OK, tap Clear
data, and tap "OK".
6. Tap the Back button to get back to the
applications list.
7. Scroll to and tap Google Service
Framework (or Google Play Services)
8. Tap Force Stop, tap OK, tap Clear
data, and tap "OK".
Now reboot (switch on & off) your device.