Regression of r75407, Exiting "Bound Around Demo" from fullscreen leaves black borders around the desktop

0.4.11-RC-30-g83e4a61 gcc dbg + VBox 4.3.12 + VBEMP + inbuilt Mesa
"Bound Around demo" from rapps

Reproduction steps
-set desktop resolution to 800x600 32bpp
-start the game in fullscreen (this is default)

Observed result
when you exit the game, it will not properly restore the desktop. It leaves black borders to the right and to the bottom. These can be workarounded later by changing the desktop resolution 2times via desk.cpl
0.4.11-RC-30-g83e4a61__blackBorders.webm
0.4.11-RC-30-g83e4a61__blackBorders.log

Expected result
Windows XP SP3 ofc properly restores the desktop without black bars.

I experimented:
When I apply revert_r75407.patch to the same ros revision, then the desktop is properly restored.
I set guilty revision therefore to SVN r75407 == git 0.4.6-dev-g09ab5ea7ed2ab0e709ed2e8f8f9f6c3711b2ac7f.
Please notice, that filed guilty rev is most likely just an unhider.
I suspect the real bug to be in our explorer.exe.
0.4.11-RC-30-g83e4a61__reverted75407_noBlackBars.log
0.4.11-RC-30-g83e4a61__reverted75407_noBlackBars.webm