yep dvi-vga does not work
remember we are hitchhiking on 4000 drivers in OSX, which are meant for 1 dvi + 1 mdp, so we are lucky dvi works at all on 2nd port.
this has been left out pretty much but for the simple reason that no one bothers to run VGA displays for such a beast like the MacPro
wait for your dell and it will probably work (if its dvi)
now added info in main post, "what works and what doesnt"
Now it's much more clear. I can't image the vga driver thing.
It's true "no one bothers to run VGA displays for such a beast like the MacPro". I'll try with the dell.
Sorry for the waste of time and thanks.