Just a guess, you might want to check and see if the previous version was completely uninstalled (meaning files and registry entries). I've gotten this type of an error before when an application wasn't completely uninstalled in the registry, (thank you msi) but all the files were deleted. If this turns out to be the case, you have to go in with regedit and delete the msi entries still hanging around. One quick thing to check, is the application still listed in the Add/Remove programs?