No. The Microsoft Visual C++ x64 redistributable loaded without a problem.
Might be in the registry? .. Uggggh !

I thought I ran into the same problem too, but it turned out to be my mistake.

Here's what happened to me (that I think is probably happening to you):

I downloaded the update and began the install. I didn't click on the option to install an icon on the desktop because I already have one. After the installation finished, I clicked on the Vegas icon and ... boy is this frustrating, it's the same old Vegas 8b!

It turns out that Vegas 8.1 installs as a separate program since it is likely that you might want to still use the 32bit version until you get more confident with the new version. If I clicked on the old Vegas desktop icon, I still got the old version, but if I went to Start / All Programs / Sony, there were both Vegas 8 and Vegas 8.1 folders and start options. I simply hadn't started the right program.

With this in mind, I think it is pretty fair to say that Vegas 8 users who are using Vista 64 should download and install both versions, at least until we are all confident with the new 64 bit version.

Thanks for trying Laurence but that's not my problem.
I can't install 8.1 at all. Installation is stopped by the wonderful
error message ""windows installer service could not be accessed" ..
Windows installer is Microsoft's program to install or uninstall software.
Obviously Sony is using it, but for some unknown reason (and just in the
case of 8.1) it cannot be accessed on my system during 8.1 installation.
IT may be one of those bizarre registry problems as I know the installer is
working since it installed 8.0C plus I uninstalled several programs I no longer
need just to be sure installer was functioning.

Wierd! ..

Hi,

did you try a right click on the EXE and "Run as administrator" (or whatever the option is called, I'm using a non English version)? I've found that using that option does the trick in many cases.