This may have already been reported, but if it hasn’t, and if it helps others:
Avast was erroneously detecting malware in a SAS .dll file, and putting that file in the virus chest. Listing the full pathname of the file in the exclusions lists wasn’t working, until I noticed that the path in the virus chest began with "c:\progra~1", whereas the the path in the exclusions lists began with "c:\program files". Changing the path in the exclusions list to "c:\progra~1" fixed the problem.