At least for now, for those who may be thinking of trying it, do not use Vista to do firmware revs to your Audiovox / UTStarcom devices.
The update from Verizon and UTStarcom for the XV6600WOC (http://www.utstar.com/pcd/downloads/HA_VZW_207_112_01167_A12.exe) will run in XP SP2 compatibility mode as administrator but in my experience with it today I only got as far as wiping the old firmware off the device. At that point the Windows Mobile Device Center did not complete the process. In my case I ran the cradle over to my XP Pro desktop, installed ActiveSync 4.2 and was good to go on that system. The installer for the firmware picked up where the initial run on Vista failed. Now I’m back over at the Tablet PC where I normally sync the device to get everything back on the 6600. So if you want to run Vista at this time, make sure you keep another box around with XP or Win 2000 on it for times like this.