WinXP Home/SP3, fully updated; SAS (free), fully updated.
Most of the time, on my PC, SAS is not running or updating, and the SAS Core Service is disabled (I use AVG as my primary antvirus).
Once a week, I start the SAS Core Service, update SAS, and run a full scan. It takes a long time because it is an old, low RAM PC with a slow processor - used only as a backup.
Recently (started 9 May, 2012) the SAS scan time has gone from 3 hours to 5 then 10 then 15 hours, and the last scan (26-28 June) took more than 38 hours (346 Memory Items, 32034 Registry Items, 41396 File Items scanned). And that was while disconnected from the all networks and the internet, and with absolutely nothing else running - even my AVG was completely disabled.
I am NOT asking for ways to shorten the scan (like excluding archives, etc.).
I want to know why the scan time has increased so much. The only changes to the computer over the period of increasing scan times have been the May and June Windows Updates (and, of course, OS stuff like restore points).
No malware is found by SAS or AVG or several other on-demand scanners.