Something is either missing or corrupt. Either it's not checking when last run or a script to initiate checking and executing is missing. I just don't know what to look for and where.
Neither do I. You could do a reinstall, which in SL gives you new system files while leaving everything else in place. Though, I'd have a backup (preferably a bootable clone) to restore from in case (shouldn't be necessary, but you always want a backup anyway.) Then update using the 10.6.6 Combo.
Just as a generic step, first run Verify Disk and Repair Permissions from Disk Utility. Just guessing like you, but maybe uninstalling Anacron took something along with it. Or, maybe, the uninstaller missed something? EDIT: You could get EasyFind and search for any remnants. Enter "anacron," the name of the developer or anything else that might be connected.
http://www.devon-technologies.com/products/freeware/
EDIT: In Snow, the periodic scripts live in /etc/periodic. You can have a look there by using Go>Go to Folder from the Finder menu. You might then compare what you're seeing enclosed in the three folders, daily, weekly, monthly to what's on your wife's Mac. Anacron would have run the scripts from /etc/crontab I believe, which no longer exists. You shouldn't be seeing crontab there.
http://alastairs-place.net/anacron.html
See Kappy's instructions to uninstall Anacron.
http://discussions.apple.com/thread.jspa?threadID=2525803
Message was edited by: WZZZ
Message was edited by: WZZZ