I have been using Mystic Thumbs with Opus for years, now, However when I upgraded to the recent and latest version I started to have real trouble. Opus would take 100 per cent of the processor for minutes on end, leaving my machine unusable. As soon as I reverted to the old version the problems went away. So just beware.
Do you mean the problem started when you updated Mystic Thumbs, or Opus?
If Mystic Thumbs, have you reported it to the people who make it?
I have been using Opus 12.6.1 since the beginning of the month with the old version of Mystic Thumbs. I upgraded Mystic Thumbs this weekend and started having the problems. To my mind the problem is with the new version of Mystic Thumbs. When I get the time I will report it to them. The old version is working fine with 12.6.1 and gives be the transparent pdf thumbnails I need, so I am not too fussed.