This situation has been posted before on various forums and the resolution/workaround has been tossed around as to the way to get around this situation. The problem presents itself when your iPad notifies you that you have updates available for your installed apps. However, when you click on your App Store and then Updates the page simply shows as blank with no apps listed.
There appears to be no true “fix” for this situation. For some the fix has been hard rebooting their iPad and then when it comes back up, the App Store displays correctly. However, the other day I had a client with a 3rd generation iPad that had this exact symptom. He showed to have 8 updates and then none showed up on the updates page.
The hard reboot did not work either. However, the “workaround” for us in this situation was simply choosing the Purchased menu in the App Store instead of Updates. This page shows you all the installed apps and then next to the app, it will have the “Update” insignia if there is an update available. You can simply scroll through your list of Apps and manually update the ones that have an update available. Ironically, after we performed the manual update of the apps in the app store, the next update we had come available, it displayed correctly under the Updates menu.