I recently had to reinstall XP, & after reinstalling Dopus & importing my old prefs file double clicking the desktop no longer opens a lister.
I've checked the settings & can see no reason why it's stopped working, if I double click the taskbar icon that works ok, but I'm so used to dbl clicking the desktop it's driving me nuts.
Any suggestions welcome!
Have you checked that Preferences, Double-click, Desktop, Support double-click even if Active Desktop (web content) is enabled is on?
Check Preferences, Layout, Opening Listers as well as the Double-click section in case there is a conflict. (I'm not sure if it's possible to have such a conflict, but it's worth checking.)
Also note that double-clicking the desktop only works when Opus is already running in the background, so if your new install doesn't have Opus set to run automatically it won't work initially.
Yep all checked & all ok, & Dopus is running at startup.
Does it work if you right-click the desktop and select New Lister from the menu?
Yep, it's just the double click that won't work 
Hmm, strange. 
I'd try reinstalling Opus in case the wrong version of a DLL is left over somewhere but if it's a completely fresh install then I don't know.
Definitely whacky ... I know you've 'verified' the double-click settings, but can you try actually 'changing' some of the settings and relaunching Opus maybe? Disable double-click on desktop, exit Opus from the systray, relaunch it, re-enable it, and try again etc etc?
Clutching at straws, perhaps, but could another started task be intercepting double click? Might be worth selectively disabling other started "stuff" to see if that is the case.
Cheers, AB