Thank you very much for your quick response George.
I looked around the forum and found another solution.
It is to mark the first chapter point marker (#1) so that it becomes red. Then just move the CTI to the frame you want to set as a "different" poster frame (or the loopsegment start), then right-click and then set poster frame.
In this way you have another frame as the poster frame than the first bright frame of a chapter point.
In my case I had text in the chapter point, but wanted a photo or frame of the movie in my video thumbnail.
It became really nice and works well! :)
Problem solved! Cased closed! :)
(I saw that someone mentioned that this was only a Encore 2.0 feature, but I have 1.5 version, and I hearby confirm that 1.5 version may do this as well. Just remember to click on chapter point (so it is red) before you move the CTI and mark the new frame!)
Thank you very much Creative Cow for this tread it helped me out:
http://forums.creativecow.net/readpost/145/858590?
Regards, and stay CREATIVE
Bjorn