ATI Radeon 9600 Pro rendering issue

[Da Snoop]

GZDoom: 1.1.04

CPU: AMD Athlon XP 1600+ (1.4 GHz)
RAM: 512 MB (SDRAM)
VC: ATI Radeon 9600 Pro (256 MB / 128 bit)
Drivers: ATI Catalyst 8.8
Monitor: ASUS VW192S (16:9)
OS: Windows XP Home (SP2)

I can't launch the GZDoom in OpenGL rendering, since there's nothing visible after the startup screen. The GZDoom window stays filled with white color or is translucent at all, showing the desktop in background (just the window borders are visible). The title music is playing and I can hear the sound when I hit the cursor or ESC key(s). I can even get into game when I hit Enter key repeatedly and I can hear the music.

When I quit the game (F10, Y) and launch it again, it loads up in software rendering. Changing the renderer in Video Options doesn't help. I can change it to either Software or OpenGL, but nothing happens even when I change the resolution. It's allways software. Also the GL system in Display Options is enabled (not disabled as I'd suppose if GZDoom runs in software mode).

I'm using the same ATI drivers as before (I've had to reinstall WinXP) and they're the latest available. Before the OS reinstall I ran GZDoom in OpenGL (1280x720) without a problem.