I did see it, actually, but only after automatic updates tried to install it & failed. Absence of apparent adverse effects at the time led me to think 'no harm, no foul' - the fax issue that came up a couple of weeks later related to an interaction between the fax software and the TWAIN interface, which the fax software tech folks thought had nothing to do with .NET. They were very surprised to learn the problem had been fixed by reinstalling the .NET frameworks (only versions 1 & 2 - yrag advises XP can't really use 3.5 or 4 anyway).
A curious coincidence -
At about the same time I started having trouble with my fax/scanner issue at home, all three workstations at my office which use Fujitsu scanners for scanning in documents began having similar problems with significant delays between pages on multipage scans and massively bloated scanned file sizes (a 4 page .tif file which should be ~100k would end up 1.5MB) after having had no such issues for 18 months. This has also been associated with a very noticeable change in responsiveness of the remote desktops to which we VPN - typing lags, post-click delays, lockups. Not sure how/why there would be an impact within the virtual environment, but there is a lot of interaction between it and the local desktop for certain functions, scanning in particular. These workstations have automatic updates set for unattended D/L & install of security updates (since staff ignore them like an old boyfriend) - no installation error on any of the machines like I ran into at home, but the coincidence seems a little too cute and I'm going to run through yrag's drill on one of the workstations as a test to see what happens.