(Edit much later: Didn't realise that Jon posted something very similar just before me. Sorry.)
I can't see anything in the 9.1.0.3 (latest version) change log relating to that. Could you paste the relevant line and say which version it's from if it isn't 9.1.0.3?
Just PowerDVD or any program?
For what it's worth, I watch DVDs using PowerDVD on this computer every so often and have rebooted with the DVD still in the drive without seeing any prompts. Do you have any other software involved with DVD playback such as AnyDVD or similar? (I also use AnyDVD, but on a machine that doesn't have Opus on it.)
And that's Opus's fault? Have you reported it to CyberLink?
It's certainly not normal and does not happen here. It sounds as if PowerDVD playing the disc makes it appear to be newly-inserted into the system.
I would check your autorun/autoplay settings as it is almost certainly them which is launching Opus. Why autorun/autoplay is being triggered by you playing a movie in PowerDVD is difficult to say but Opus is almost certainly being launched by something else. Opus, by itself, will never open a new window because a disc was inserted (or appeared to be inserted) so you will need to investigate what is triggering autoplay/autorun to do so, and/or configure autoplay/autorun not to do anything when discs are inserted.