I just learned from Neat Receipts that the problem is caused by a flaw in the way that Windows Vista handles the migration of settings and files from a previous Windows XP instance. This might occur if your Vista install was an in-place upgrade over XP, or if you transferred a previous user profile.
Windows XP uses a file called layout.inf, which lives in C:\Windows\inf. This file, which is generated when the operating system is installed, contains information about the location of Windows system files. Windows Vista does not, by default, include a copy of that .inf file. It stores the locations of these files in an entirely separate location.
If a Windows Vista computer contains a copy of this layout.inf file in the Windows\inf directory, a number of devices will fail to install. Browse to the directory C:\Windows\inf, find the file layout.inf and rename it to OLDlayout.inf, then attempt to reinstall your scanner driver. It worked perfectly for me.
