Try putting your ethernet card in different slots. you want video and usb closer to the motherboard connection side and the sound and ethernet a bit farther away,at least thats how it works for me. As far as i know you dont need to allocate anything off the video card, the devices use the ram automatically.I use SMC 1211TX cards for fastethernet myself.
As long as you have a hardware definition setup calling fastethernet.device you should be able to query the card in miami.
Also check any jumpers on the mediator for correct orientation.
Mech
