So the fix is registry magic!
In this register tree:
there is at least an entry per monitor; I had a DELxxxxxxxxxx and an ACRxxxxxxxxxx one, and under the 00 node, there are two parameters to check out there:
PrimSurfSize.cx, PrimSurfSize.cy and Stride.
These should match your current monitor.
A little below you should see these entries:
inside, you will also find under the 00 node, and those parameters pointing to the old sizes. Use the values from above, and also change under the remaining 00 node the ActiveSize.cx & ActiveSize.cy entries to match. Log off or restart and voila!