Hi, I have similar trouble.
Card: 7600 GS PCI-e
Monitor: ASUS VW222
System: debian 4 lenny, amd64
If i run games on 800*600, and use "Aspect ratio scaled" without "Force Full GPU Scalling" option -- the black bars, which have to appear, but some part of image is out of visible area.
If "Force Full GPU Scalling" option in turned on -- no bars have appear, image scaled, but its look like "Fit to width", and bottom part of image -- is invisible.
I try to set 4:3 in my monitor but this option is disabled. This is no problem of monitor.
When i run games with 800*600 resolution in Windows: image is really Aspect ratio scaled, and I can switch between 16:9 and 4:3 mode in my monitor`s menu.
This is driver bug?