My Apps now appear to be updating ok. I suppose it was the earlier referenced MS server issue and they've now managed to fix it.
Having said that, I think the syncing of apps between my laptop and my Dell tablet maybe a little screwed up - In Windows Store, Account, My Apps, selecting 'Apps...
I'm also being affected by this problem, exactly like ssbtech. Like you guys, it only seems to have happened since I allowed my last batch of updates to install a few days ago. Can't find much yet on this except for generic suggestions such as running MS's 'AppsDiagnostic.diagcab' tool...