It is happening on updates and new apps. Seems like everyone. The only way I have been able to clear it is to have iTunes do the installs and updates. This becomes a problem when I'm at work or out and about. Heck, just sitting in bed and looking for new stuff to play with beco es frustrating.
I have just solved this issue by pausing two podcast downloads which have been stuck. For some reason those pdocast downloads got stuck and due to this i was not able to install new application . After pausing them the applications can be downloaded without problem.