After waiting a while, I checked back in...
I must confess to being more than a little disappointed to find that MC17 development has now been concluded, and this issue was never fixed. I bought MC17 as part of the "early adopter" program to upgrade from MC16, but I was never able to use it because of this issue. I'm still using MC16, so my money was thrown away basically.
Yes glynor, my symptoms are still essentially the same as you describe. I've posted specs (7x64, Core i5 4GB, Radeon HD4600) and JRMarks (3137) before; it's a fast machine and is dedicated to JRiver, no other software essentially except for DBpoweramp for ripping. So speed isn't the issue. This is a problem that appeared, as I said, midway through MC17 development. Early MC17 versions were fine, as is MC16. I now have tested MC17.0.183, Catalyst 12.6. These latest versions have the same problem I have reported all along.
MC16 still works fine. Somewhere along the way, the video output routines in MC17 developed a problem, and it has never been fixed. It's that simple.
Not sure if there's any reason to believe it will be worked on in MC18.
This is very frustrating for me. I would like to get what I paid for. I would like to be able to support further development of JRiver MC18, and enjoy the new features that MC17 and MC18 will provide. I love the software, and I think the company is a great one.
But I need the software to work properly for core functionality. I will not through good money after bad.
If this issue is resolved, I would gladly purchase an another upgrade.