Steam IL2 Sturmovik 1946

[nuNce]

Hello,
I've bought Il2 1946 by steam yesterday. The game launches perfectly, and I can play it fully, but I have some resolution issue. First my system:

Athlon II X2 240
Ati HD4670 512Mb
3GB Ram
Windows 7 Ultimate (yesterday played on XP same issues)

I have a 22'' Asus monitor with a native resolution of 1920*1080. I found out how to set the resolution in the conf.ini file, but when I do so the textures in game get corrupt, checked black and white, completely white, or green (wich doesn't happen when I use ingame standard resolutions), both if fullscreen or widescreen. When using 4:3 resolutions in fullscreen the image gets streched, so I can't play it that way. Also, when going fullscreen with a custom resolution (like 1280*720) the image just partly fills the screen and I can see the desktop behind it.