Raumohir the hsitory information for ObjectBar indicates that it should be compatible with Vista. Two thing's may be possible, bad download or it is a limitation of the trial version. Try uninstalling, run a clean up program like CCleaner and reboot. Reinstall ObjectBar and reboot again. If it still doesn't work it could be as I said a limitation of the trial version.
Just out of curoisity why aren't you using the Vista Sidebar? Or are you wanting to use both?
I'm on an XP system, have checked out ObjectBar, but I find using ObjectDock more to my liking. Yea I know they are not the same.