I have tested again.
In a short article (4 pages) everything works just fine in horizontal and vertical layout.
However in a long article (41 pages) the vertical scrolling of text in the horizontal layout simply doesn't work except a one exception. I have checked all the settings - they are identical.
The strange thing is that if I preview the horizontal layout in the ADOBE Content Viewer all the scrolling works just fine, but as soon as I add the complete article consisting of horizontal and vertical layout to the folio things stop to work.
This is really frustrating. Maybe it's necessary to re-think the layout and avoid scrollable content since it so unreliable.
Right now I have no idea how get this to work.
The tools I use are: InDesign CS5.5 on OSX 10.6.8, FolioPanel-CS55-12_1_3, FolioProducerTools-CS55-1-9-1
Any help would be apprechiated.