Boot Scan and Full Scans stall and do not complete

New user of Avast 5.0.396, replacing Norton.
Quick Scan works fine.
First Full Scan found a virus and removed it, but never completed.
Subsequent Full and Boot Scans run consistently to about 90+%, in 45+ minutes, scanning about 63500+ files, then simply stall. File name, byte count, completed file count don’t change; run time increases and Speed (bytes/second) decrease. Would stay that way for hours if I let it. Tried this 5 times now.

I see what might be related or similar posts, but for those I’ve checked, dialog always seems to stop before a solution is posted.

Clues anyone?

Please go into the settings of the Full system scan - and on the “Report file” page, enable creation of the report file - and let all possible items (even “OK items” and “Skipped items”) be included in the report. Then, run the scan again.
The resulting report will be rather huge - but when it stops again, it should be possible to say (according to the end of the report) where the problem is.

Only got 2 reports from 5 scans, possibly because I stopped other scans manually. Hundreds (thousands?) of skipped files, and last entry on both logs is for the same skipped file.

So, you already enabled logging of “OK items” before? There should also be many of them in the report…