I have tested this command with a cmd launched by local system (like Landesk does), and it doesn't work, so the problem is here.
Why it is not working with local system user ?
lol Philipp, your link is my own thread on lenovo forum
The answer given doesn't change anything
Funny thing, 5 minutes before I received your answer on our case, I was talking to my responsible about that case opened since 03/2011, I was about to close it, because I have changed from UMA to USMT
I suggest LANDesk to remove UMA from LDMS as it does not work with windows 7 !