1 GB of RAM for the SuSE 8.2 install is fine (that's what I have in mine). It's more likely a problem with the video card. Isn't the FX5800 one of those with multiple video channels ? Perhaps the output appears on the wrong one (not the one were your monitor is attached).
On the Radeon 7500 that I had in the system at install time the same picture appeared on both the VGA and the DVI output.