Everything mentioned in Problems installing Opus is worth a try, even if the error message you're seeing is slightly different.
For some reason, InstallShield's can show a different message for the same type of error sometimes, but one of those fixes almost always works. (That said, the message you're seeing is most similar to the 3rd suggestion, so I would try that one first.)
Have you tried all of the suggestions on that page already? If not, please try them and let us know what happens.