MSI bundle forces a reboot

I'm installing a program using an MSI that prompts the user to reboot the computer at the end of the installation. When I run the command from the command line I get the prompt to reboot (yes/no). I click 'no' and the computer does not reboot. When I duplicate the command line in zcm I do get the same prompt, but when I click 'no' the computer REBOOTS!! The command line that I'm running is 'msiexec /i xyz.msi /qb+!' Has anybody else seen this and if so how have you gotten around it if at all? Oh, yes I have tried REBOOT=ReallySupress.

Thanks for your help!!