On my Ipad2 I have 5 apps with an update available. When I select to update and give my password the app symbol just shows "waiting". No download is occurring on anyone of the apps in question. This just started yesterday, I've rebooted and re-synched.

Are you sure you're connected to a network?

Also check that you are using the same iTunes / App store account to pull the updates that you used to purchase the apps.