I was suddenly having severe performance problems when browsing network directories when using the Windows Explorer.
The Windows Explorer would slow to a crawl and often lock up and fail to respond.
My first thought was that Avast was scanning each executable when the directory was opened, but as it turns out, that was not the case. ???
The real culprit was one, or more, bad Windows Explorer thumbcache*.db files for the network share being browsed. :o
They are located in the “%USERPROFILE%\AppData\Local\Microsoft\Windows\Explorer” folder.
The fix is to delete all the possibly bogus Windows Explorer thumbcache*.db files but note that these files are usually locked for security reasons.
Several free utilities are available to delete them. Don’t worry, Windows Explorer will rebuild them when needed.