This was copied from the blog:
As we update our customers to SP1, we want everyone to have a great install experience. We are going to stage our rollout of SP1 for current Windows Vista users to be approximately concurrent with the availability of Windows Vista SP1 on new PCs and in stores. There are a couple of reasons for this. Our beta testing identified an issue with a small set of device drivers. These drivers do not follow our guidelines for driver installation and as a result, some beta participants who were using Windows Vista and updated to Service Pack 1 reported issues with these devices. Because the issue was with the way the drivers were installed and not the drivers themselves, the solution was simply to reinstall...