Currently using Avast/Free 5.0.507 w/Eng,virus 100415-0. The program will automatically update, as it did this AM. But, have it set to auto scan @ 00:00HR CDST, and it won’t. scan. Was working fine last week, but now something is wrong. Gremlins in system?? Any help would be greatly appreciated. Thanks…
Welcome to the forums, QBALL263 
Have you tried deleting the scan setting and making a new one?
If that does not work, try a repair of avast.
You did not tell the OS but here is how to repair using XP. Others should be similar.
Control panel > Add/remove programs > click once on avast to select it > click on Change/Remove > scroll down the left pane and click on repair > click OK > follow directions
Just a thought, when you set the Schedule, did you also set the Wake up the system to start the scan (if in sleep mode) ?
Otherwise if your system is using power saving and goes into standby, perhaps that is why the scan doesn’t start.