@ jl747, DavidR,
First picture attached is a pop-up window that shows up when the main gui is minimized.
The only time I see this scan 99% error is when avast gui is minimized. At no other time do I see it. When it does, scan has completed normally.
All other scans done, when the gui is on the desktop, run and complete normally.
Testing done to isolate when and where the gui error occurs. ;D