InstallShield crashing when run from a remote machine using STAF

I have been using STAF/STAX for a while now as a framework on top of software test automation. When we started moving some of our tests in Windows Vista noticed that there have been cases where uninstallation of the software under test is crashing. I thought it was some component not playing well with Windows Vista but I when I tried to perform the uninstallation sequence manually everything was fine and dandy. So I started digging around and I found out that in Windows Vista, the following command may fail.

C:\>staf remotemachine process start command "C:\PROGRA~1\COMMON~1\INSTAL~1\Driver\1150\INTEL3~1\IDriver.exe /M^{1CD6500F-DE1E-44AC-A279-4C85247A9A85^}"

Poking around even more and I finally found a workaround, to get the above command working in Vista, do:

C:\>staf remotemachine process start shell command "C:\PROGRA~1\COMMON~1\INSTAL~1\Driver\1150\INTEL3~1\IDriver.exe /M^{1CD6500F-DE1E-44AC-A279-4C85247A9A85^}"

Notice the use of shell to make this command to work. I would have loved to know why this is causing problem in Windows Vista and not in XP/W2k3.

~ts