Hi Martin,
DId you open a ticket at
https://mantis.arcanoae.com to ask Arca Noae ?
Based on my time working at Mensys I can partly answer your question. It does matter if you *NOT* (post updated!) use Panorama, the IBM GRADD or SNAP driver. All of these drivers are GRADD (a graphics driver model from IBM). The driver that provides the video support for DOS and as far as I can tell WIN/OS2 support as well is VSVGA.SYS.
Just an educated guess. On eCS 1.2 you where running an *older* computer with a different video card.
You see VSVGA.SYS as far as I understand it is very depended on the video hardware .
Infact as far its clear to me, even when you run SNAP with a native video driver (that talks to the video chipset directly)
the video support for VDM's (DOS and WIN/OS2) is still provided via VSVGA.SYS.
This can also explain WHY the video performance of WIN/OS2 is not that fast.
The reason you see certain video modes (such as seamless WIN/OS2 ) not working is depended on the video card you have.
Try this switch:
http://www.edm2.com/index.php/VSVGA.SYSBut it will most likely not resolve your WIN/OS2 issue.
Roderick