error pushing 2008 SP2.1 out to Vista - admin installation

When trying to install SolidWorks 2008 SP2.1 on Vista from myadministrative install, I get an error message:

A program required for this install to complete could not be run.Contact your support personnel or package vendor. Action:userpref_registration, location: C:\Windows\, command: regedit /s"C:\Program Files\SolidWorks\lang\userpref.reg"

and the same thing is logged in the application log:

Product: SolidWorks 2008 SP02.1 -- Error 1721.There is a problemwith this Windows Installer package.

regedit.exe is in C:\Windows, and the userpref.reg file is inC:\Program Files\Solidworks\lang\userpref.reg, so I can only assumethe UAC is preventing this from running? After hitting OK on theerror the installation errors out completely. Afterwards, I candouble click the .reg file after this prompt and add the info tothe registry just fine but it's a little too late at that point.This exact same script installs fine on XP, any ideas?SolidworksAdministration