I don't know if I'm the only one experiencing this, but my Opus help file (you know, the one brought up by pressing F1) periodically goes missing.
To get it back, I have to reinstall Opus. Usually a simple reinstall over the existing version works just fine.
I don't notice it often, but it's happened a couple of times in the past two years.
Sound familiar to anyone else?
Missing?
When I go to Help » Help or hit the F1 key, nothing happens — no error message, no new process created (as far as I can tell), nothing.
I would've checked to see if the help file itself still exists, but I'm not sure where to look.
My best guess would be that a missing help file would still result in some kind of error dialog, and since a reinstall restores the ability to call the Windows Help file for Directory Opus, I suspect it's a registry entry that goes missing.
See if the CHM file is still under /home/Help (type that into Opus).
If it is, try double-clicking it.
It's there — but I went ahead and reinstalled Opus over my existing installation earlier when I noticed the bug had resurfaced. 
I wasn't thinking about troubleshooting it at the time, so I just defaulted to the solution that had worked for me in the past.
Now that I know where to look for the help file, though, I can check next time my F1 functionality goes AWOL. 