NAV 2009 - Taskbar Symbol missing and not starting for normal users (admin works)

Hello!

I own a license for 5 installations for NAV 2009. While it works on one machine without any problems (XP pro) it has severe problems on two others (XP Media Center and XP home):

While Administrators can start the programme without any problem and do have a taskbar symbol, "normal" users neither have the symbol nor can start the programme. As I thought, this is a problem with windoes rights management and used Sysinternals programmes to monitor failed accesses on files and reg keys. I found no major differences between Admins and Users.

So, what might be the problem and a solution?

Thanks a lot!

A.borque