Windows Vista has all sorts of great new security features.
One of them is User Account Control, which is designed to limit a user's ability to operate with administrative powers. This should prevent some exploits from jacking up the machine.
However it frequently prevents apps from running properly. This is due to many legacy (and some new) apps requiring Administrative privileges to run correctly.
The first thing I try when an app fails strangely in Vista is to right click the app, and run as administrator. You can also go to properties, and set it to always run this way.
But if that is not good enough, you can disable UAC, by doing the following:
go to control panels, user accounts, and disable User Access Controls.
This will require a reboot to take effect.