I haven’t used 5 on a Vista machine (it is not supported) so I do not have a definitive answer on this however I will venture a guess. If you used to be able to do this in Vista and cannot do this now more than likely a microsoft Vista update has been installed that broke this functionality. If it was recently that you could do this, try going back to a system restore point before it stopped working and see what changed on your system between then and now. Notice what hotfixes were applied and what add-ons were installed. Once you narrow it down, you should be able to remove the culprit.
You may want to consider moving up to Vegas pro 8 which is made to work on Vista if you are going to continue working in a Vista environment.
j razz