I tried "scan local drives" from the menu, made sure that nothing else was running (including stopping TimeMachine) and left it overnight. When I woke up and woke up the mac, the beachball was spinning, and I could not switch to any other program. I can't force quit, and after clicking in a few places, even the beachball cursor has disappeared. What can I do? It didn't report any threats, and it doesn't appear to have scanned much. This is a big problem. Is this a common problem? Is there a fix? I have an early 2007 MacBookPro Core2Duo with 3GB RAM.
Update: Had to force a reboot using power off. I told it not to look in archives, and tried to run it again. Part of the way into it I needed to look at something in a browser. OK for a few minutes then... Spinning beachball. Cannot switch from the program, cannot cmd-tab, cannot get the tray or the menus. Will have to force a reboot again using power off. I have succeeded in getting it to do a scan of a folder, but scan local drives always makes the machine hang. I will try again where I disconnect the network... frustrating, and time consuming.