Click fails to open folder

Recently I've started having a problem where a left click on a desk top folder does nothing. Also, a left click on start menu folders does nothing. Right clicking a desk top folder and then selecting "Open in Directory Opus" does nothing. Clicking on the Directory Opus icon on the start menu does nothing.
Directory Opus runs and opens a folder on start-up. (It never used to do this). If I close the lister, the only way I can get it back is by clicking on the task bar icon and selecting "Open new lister".
I suspect that the problem is some incompatibility between the latest version of Directory Opus 10 and some other program that has a recent update.
I use Advanced System Care Ultimate 8 as a virus protection program. I added dopus.exe to the white list but that has not made any difference.

Try adding dopusrt.exe to the white list as well (or just temporarily disable the virus checker if you can, to see if it's involved).

Also, make sure you have not marked Opus to run as administrator (elevated).