Hi and welcome to the forum.
Could be because your program is out of date. Current program version is 4.8.1296. Try manually updating the program (right click the tray icon, select “Updating” then “Program update”.
Should do the job.
Could be a sizable download, BTW, just in case you’re on dial-up.
Well error code 0x00000002 (2) is I believe a file system error and ti means “The system cannot find the file specified.”
So there is something wrong with your installation of avast, so added to that your having an old version of avast, I would suggest you do a clean reinstall of avast.