You might see if toggling thumbnail previews
off an on may reset it to show properly afterwards.
No, the tcpmon.ini
file wouldn't have anything to do with this. However, here is a clean copy of it below to replace your corrupted one with. You would just need to take ownership
of your C:\Windows\System32\tcpmon.ini
file and "Allow" "Full Control" of it to your user account, then copy and replace it with the new one.