Hello. I'm running 9.1.1.0.3156.x86 and I have recently found that the software goes into a loop at random intervals. Happens every couple of days.
I use Task Manager to stop dopus and dopusrt, but the when it's happened once, it's almost certain to happen again and again until I reboot.
Something I do see is that "I/O Other" is rocketing up at the time - so even though dopus is unresponsive to the user, it's doing something wildly in the background.
It is most likely to be either real-time anti-virus scanning, video codecs or shell extensions, most likely doing something disk or CPU intensive in response to Opus opening the files in the folder you are viewing.
Opus will open the files to generate data for columns like Description, Width, Bitrate, etc. It may also open some types of file to get their icons. (e.g. If you have a very large EXE file, such as the installer for a big program, then a real-time anti-virus program may scan that large EXE when Opus reads its icon. I've seen that this can take quite a long time with the scanner that I use on some setup EXEs. I guess it's unpacking the contents of the installer, than recursively scanning all of that.)
If you use Process Monitor the next time you see the problem it may make it obvious which file is triggering the problem (it'll be the one which dopus.exe is reading from a lot) and that in turn may make it easy to work out how to fix it.