Ok, I've been looking around and have found a few people that run Vista and play both 2k3 and XP without any problems, although all of what you said seems to lead to a problem with Vista.
Vista is a new program and certain bugs will not have been found as of yet, while some people may have no problems in a certain area, others may. If the version of 2k3 you downloaded works on other operating systems, and you have installed it correctly then it sounds like a problem with Vista.
It would be more assuring if i didn't work completely as it still may be something wrong with what your doing.
Try this: bring over an old already created project and see if you can open it. If you can a quick solution would be to make an empty project on another computer, save it to disc and just duplicate the project every time you wish to start a new one.