This is going to sound weird, but...
I just rebooted the system for quite banal reasons (GDMFSOB Adobe updates), and when I tried to use one of my context menu shortcuts to start a "dos prompt" in a standard folder, instead of the application starting as it usually did, I now get my text editor displaying a blank text file called "C:\Program"
Now, the actual application that shortcut linked to is (without any quotes):
C:\Program Files (x86)\JPSoft\TCMD\TCMD.exe
Other shortcuts referring to a similar folder and application :
C:\Program Files (x86)\JPSoft\4NT8\4NT.exe
suffers from exactly the same problem, but only in Opus!
Now, I can assure you that I have NOT done anything to either of those applications, nor their folders, nor anything about them in at least a year.
I have also made no changes to DO in the time when I last used the menu items (yesterday) and today, and I've certainly not edited any of the shortcuts.
There have been no changes to any default application executions, no changes to my profile, and definitely no changes to anything explorer-related (that I'm aware of, anyway).
I've not touched any registry keys, nor anything else related to Opus or the two applications involved here!
I verified that both the shortcuts are listed and displayed and entered correctly in the context menu items, and they are - but for some reason, they no longer work!
FYI, I can run those applications from other shortcuts elsewhere on the system - for example, from the start menu, from Workshelf (Winstep extreme UI enhancement) and from explorer.exe's context menu.
The last time this happened to me, it was because some stupid shareware POC tried to create C:\Program as a folder because the inbred developer didn't know how to handle spaces in filenames (just this year, in fact). Bit I've double-checked, and there's no such confusing folder that could be tripping up Opus (I hope!). Having said that, because this is an x64 OS, there are separate folders for x86 apps (\Program Files (x86)) and x64 apps (\Program Files), but Opus has never had an issue with that before now.
If anyone has any ideas and/or suggestions, I'd be very happy to hear from you!