Realtek RTL8201N? There's a Tiger kext but Leopard isn't fully supported.
http://forum.insanelymac.com/index.php?showtopic=73317&hl=RTL8201N

In safe mode, go to /System/Library/Extensions/ and search for GeForce.kext, Ge*.kext, NV*.kext.

Reboot then you don't need to boot in safe mode.
But you will be stuck in 1024 x 768 resolution like me. I also have 6150 onboard. >_>