Apparently many of us afflicted with this problem saw it spontaneously resolve today after a reboot. Some had to do the following:

- Clear the cache of the Google Play Store app (Menu > Settings > Applications > Manage applications > All > Play Store > Clear cache)

- Uninstall updates to the Google Play Store app (Settings > Applications > Manage Applications; select "Play Store" under the "All" tab/filter, and touch "Uninstall updates"

- Clear the Download Manager cache and data (Menu > Settings > Applications > Manage applications > All > Download manager > Clear cache and Clear data)

- Clear the Google Services Framework cache and data (Menu > Settings > Applications > Manage applications > All > Google Services Framework > Clear cache and Clear data)

- Reboot

On my Rezound, simply rebooting solved the issue. After reboot the Play store was completely back to normal. On my tablet, I had to perform the above steps first.
-copied from google and it works.