Just a novice and unsophisticated user here. On an older IBM Thinkpad 765L, using Windows 98SE with all updates, I experienced the same issues.
I followed all of the friendly advice here on the forum (rigorously clearing out McAfee, cleaning out the new Avast) but still had the same problem.
So, I uninstalled Avast again, and per advice elsewhere in this same forum, but in different topic string, I installed Avast Version 4.7.844 from the
www.filehippo.com site. I configured to use ONLY manual updates, did my initial scan, and shut down.
I restarted and the problem with the resident and with the "A ball with red circle and backslash" were gone. Unfortunately, this will in the long term, limit the operation of Avast. Plus, I have yet to see how I fare on reloading Spybot. Plus, I have yet to download the latest Avast virus definition file.
Still, it is a "temporary fix" that others have tried successfully, and now so have I!!!!
Good luck