bob3160: I've tried your suggestion but it still won't work. I've already uninstalled, rebooted, reinstalled again, but to no avail.
Vlk: Ok, now the problem just got bigger. On-demand scan doesn't work as well. I get "Unknown error. Scan Completed with error: 87 = The parameter is incorrect.
I've tried to stop and restart avast, and there was no error message until I actually clicked on the avast icon in the system tray, and when I try to run an on-demand scan.
Thanks for the speedy response, guys.