I’m not a Windows 98 expert neither a debugger one… :-
But, why don’t you try just simple actions and try to repair your installation?
Go to Control Panel > Add/Remove programs > avast! antivirus > Remove
Then choose Repair function in the popup window (Repair).
You must be connected to the internet while repairing.

If this does not help, can you uninstall / boot / install / boot again?

Do you have any other antivirus installed in your computer?
Did you have in the past? Which one?
Do you use a firewall? Which one?

Welcome to avast forums :smiley: