Try this solution for this issue on iPad2:
Ensure that you are connected to your Home Sharing wifi network.
1. Completely close the Video App and all other open apps (Double click home button. All open apps will appear at the bottom of your screen. Touch and hold any app to activate App Management - the App icons will begin to shake and show white "-" in red circles at the top left corner of each app icon. Touch the "-" signs to close each app. When all apps are closed, tap anywhere in the darkened home screen or press the Home Button to de-activate App Management.)
2. Open Settings App
3. In Cellular Data settings, turn Cellular Data off (only if applicable to your device. You can turn it back on once this procedure is complete.)
4. Scroll down to Video settings, and DELETE your Home Sharing password.
5. Turn your iPad2 OFF (Do this by holding down the "Power" button at the top of the iPad until "slide to power off" appears at the top of the screen. Slide the red button to turn off).
6. Wait a few seconds...
7. Turn you iPad2 back ON (Do this by briefly pressing the "Power" button until a silver apple icon appears at the center of the screen.)
8. Open Setting App
9. in Video settings, re-enter yor Home Sharing password.
You should now be able to open the Video App and thumbnails should re-appear correctly in the Shared screen.
Hope this helps!