I have an annoying problem using the dual-vertical display: Double clicking a folder on either side is supposed to open its contents in that panel without opening Directory Opus a second time, right? But every time I open a folder in either the left or right panel, another program opens. Often I'll have 5 or 6 in a group on the bottom bar. The left-hand tree works OK, but not the panels. I must only open folders from the tree. I've searched Preferences and tried everything that looks like it might fix the problem, but no luck. I've also looked through FAQ and this forum. Can anybody please help?
Try turning Explorer Replacement off in Preferences, press OK, then re-open Preferences and turn Explorer Replacement back on and press OK again. That may reset the registry values that I suspect have been changed and have broken double-click.
(I'm assuming you haven't gone and edited your folder filetype's Open or double-click events on purpose, but something else may have.)