With the help of QLik Support my problem is now solved, and your problem might have a similar solution.
The windows user executing the reload (in your case the user running the qlikview services) had faulty directories listed in windows registry under these nodes:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders
and
HKEY_USERS\[userid]\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders
In my case some of the keys were pointed at nonexisting network drives. That has obviously not been a problem before we upgraded to QV12, nevertheless the solution to my problem was to point to existing folders. Qlik Support also mentioned that they have seen similar problems when such keys point to network shares even when those folders exist, and in that case the solution would be to point at directories on the local hard drive.
During my attempts to solve this I found similar shell folder keys in other places in the registry, so If you don't find errors under these exakt places in your registry you might find them somewhere similar in the registry.
