That means your graphic card doesnt support Dynamic Glow.
You can always try downloading the new 53.03 drivers (For 2000/XP) or the 53.04 (For windows 95/98/Me) Get them at www.nvidia.com
Someone told me that changing the settings may help. Right click your desktop, go propoties, settings, advance, go GeForce and there, you will get a crapload of options.
Turn some up.
PS: Try Dueling someone in r_dynamicglow 2