I don't know if this is the same exact issue, but what has happened to me once or twice is that I will have a bunch of apps that are sitting there saying "Waiting" and seem to go nowhere. I can't use the app concurrently. I have not been able to determine if it was just a matter of letting all the apps attempt to update from the iPad or not, and if it would in fact have ended up updating them all or not eventually or if it really just can't handle more than X amount of apps at the same time. I ended up syncing it to the computer which I do every couple days anyway and that of course resolved the issue. I now just try to watch how many I update from the iPad itself all at the same time. Like if 6 apps end up needing to be updated around the same time I will just wait to do a sync or I'll just update them one to two at a time instead of telling it to "Update All".