WMI filter in windows vista

hallo,

I'm not sure, if this ist the correct gruop for my question, but I couldn't
find one for windows vista.
I want to deploy a gpo depending on a simple wmi filter, that is:
Select * from Win32_Product where name = "my app"
in namespace root\CIMv2
The gpo shall install a new software only, if an other software ist already
installed.

On WinXP workstations everything works fine, but on an Vista workstation the
gpo is rejected because of WMI filtering (according to the GPMC).
When I tried diagnose this problem and installed the WMI administration
tools on a XP workstation, I just got an error, that no instances would be
available, when querying win32_products of my vista client.
On the other hand my inventory software, which scans workstations for
installed software has no problems with this Vista workstation.

Do you have any ideas, what could be different in Windows Vista?

Thanks in advance
Christian

PS: Until now it is the only Vista workstation, but this will change very
soon.