I have the same problem with downloading/updating apps directly to the phone. Additionally, when I update apps on the computer and try to download to the phone by snycing, most of the apps will not update. I get an error message. My last attempt to update apps resulted in 13 apps that would not update. I have tried every fix Apple recommends, and the only thing that has worked is to delete the app from the phone and then re-install, which is a pain.
Any help would be greatly appreciated.