I also have this problem on a "new" iPad. It updated apps fine a day or two ago, but despite the fact that now 15 apps show in the badge, the update tab has been blank for at least the last 16 hours. All other tabs for the app appear as usual, and the iPhone 5 updates apps normally. iOS is up-to-date on both devices.
I have tried the following troubleshooting steps:
- Cleared all apps from the iPad memory.
- Turned Wi-Fi off and then turned it back on.
- Turned Wi-Fi off entirely (LTE network).
- Turned the iPad off (red slider) and back on.
- Rebooted the iPad (with Home and Sleep buttons).
- Power-cycled both my modem and router.
I agree that it doesn't sound like a system restore will solve the issue. Too many others are also having this problem. Server seems like the likely culprit.