That looks like the installshield data is corrupt.
The first thing I would try is reinstalling Opus 9, in case that works and allows you to run the uninstaller normally. (Opus 9 installer)
If that still doesn't work, please see Problems installing Opus and try the second last section. (Note that the very last section is only one line, so is easy to miss. I mean the larger one above it which tells you to delete a folder of InstallShield data.)
(The very last part at the end is also worth a try: Verifying that the installer is digitally signed, in case the installer you're using wasn't fully downloaded correctly.)