I have a similar problem with that error code.
I ran the MS Fixit troubleshooter for windows store/windows update.
It did several fixes but reported that the results of the SFC scan could not be completed - a corrupt dll could not be replaced.
It didn't say directly which dll was affected; it said that information was in the CBS.log.
(to be able to read the CBS.log, the simplest approach is to copy it from %windir%/logs/cbs/cbs.log to some other folder e.g. desktop and then it will open in notepad)
The problematic file is qmgr.dll, part of the BITS download service.
This makes sense; with the BITS download broken, there is no way the store can download the app, let alone install it. However I can install normal windows 8 updates from control panel windows update
So the issue seems to do with that file, perhaps replacing that (possibly) damaged file - what's the method for that under Windows 8?
( http://support.microsoft.com/kb/929833 gives the method for Windows 7)
Anyone know the method for replacing a dll?
---update---
After an alternate account was created on the computer, that account showed lots of update in the store. These downloaded and installed OK, but any attempts to download and install new apps from the store resulted in a "this....is not available error".
The following morning, that issue has disappeared too.
Perhaps a reboot was needed to clear some residual error or complete some element of the troubleshooter that had lingered despite other reboots, perhaps there was an intermittent problem with connecting to the store. The mystery continues but the problem has passed.