In Windows 7 and Windows Vista, Vectorworks should normally be 'Run as an Administrator'.
Not only should you right-click on the Vectorworks icon and choose Properties > Compatibility tab and check the box that reads “Run this program as an Administrator” but you should also make sure under this same menu that you press "Change settings for all users" or “Show settings for all users” and check “Run this program as an Administrator” under here as well, regardless of whether this user is going to use another account or not, it helps. Some machines even require you perform the same steps on QuickTime too. Reboot the machine, then relaunch Vectorworks.