I use a small program by Stardock - Object Dock - which allows quick access to my various programs.
The dock is normally hidden with only various tabs showing. When one hovers a mouse over a tab, the dock drops down and the software icons are accessible. This worked perfectly right up to Dopus 11.
In Dopus 12, holding (or indeed clicking) the mouse pointer over the dock often does nothing. Double clicking over the dock opens a new lister. The dock is then fully functional - whilst ever that particular lister instance is open.
As soon as all instances of Dopus are closed, the dock again becomes inoperable.
Quite often, even when the original lister is open, I have to bring to the foreground said lister or open another lister to gain access to the dock.
It appears that the coding of the "double click on desktop" function to open a lister has changed in Dopus 12
If you turn off the "double-click on desktop" option does Object Dock then work OK? (If so, does turning it on again keep things working OK? Sometimes the problem is the order the different things are started.)
When the setting is on, check that dopusrt.exe is not elevated. It's also worth seeing if Object Dock is elevated, although I don't know what is normal for it. (In Task Manager, Details tab, you can add an Elevated column to check, by right-clicking the column header.) If one is elevated but not the other, it could block the two from communicating.
If there is a third program which interacts with the desktop (e.g. Ultramon is a popular example), it could also be involved and may be worth experimenting with.
Antivirus could also be blocking things sending messages to each other, particularly if it does not recognise the new Opus 12 binaries yet.
For what it's worth, the code which implements desktop double-click has not changed in quite a while.
If I disable the Dopus double click then the Object Dock responds fine. When I enable it again, (and I've done this several times) sometimes Object Dock works fine, other times it doesn't. Most frustrating! The interaction between Windows, Dopus and Object Dock is completely random...
Both programs are not elevated.
Since I can't exist with Dopus, it looks like Object Dock will have to go...
Does Object Dock or one of the other Stardock tools (maybe Fences?) have its own desktop double-click function that can be set to launch a command? If so, you could turn off Opus's desktop double-click option, then turn on Stardock's and configure it to launch Opus, which should let you keep using Object Dock and still be able to launch Opus the way you're used to.
The command to tell Opus to open a new default lister from outside of Opus is:
"C:\Program Files\GPSoftware\Directory Opus\dopusrt.exe" /cmd Go NEW
Are you using our "remove startup delay" helper (Preferences / Launching Opus / Startup) which was added in Opus 12? It's possible a side effect of that is causing Opus and Object Dock to start in a different order to before, which might explain why things used to work and no longer do (since the double-click mechanism itself hasn't changed in Opus 12).