Broadcom NetXtreme 57xx Gigabit Controller

[p-a-g]

Hey folks,
I desperately try to get my network up and running.

It's a
Broadcom NetXtreme 57xx Gigabit Controller (Ethernet, 100Mbps)
device no: Bus 2, device 0, Function 0
OEM Name Broadcom BCM5750A1 NetXtreme Gigabit Ethernet PCI Express
OEM Hardware No. VEN_14E4, DEV_1677, REV_01.

The System itself is a Dell Dimension 8400.
CPU Intel(R) Pentium(R) 4 CPU 2.80GHz
2,5gb ram
North Bridge Intel i925X Revision B1
South Bridge Intel 82801FB (ICH6) Revision B1
Network Broadcom NetXtreme 57xx Gigabit Controller
Display Adapter GeForce 8400GS 512mb

This is what I did so far:
Installed iPC 10.5.6 final. (checked AppleBCM5751Ethernet)
Managed to get the geforce working.
tried several things concerning the network.

I don't have any clue what else to do.

PLEASE HELP!

best regards
phil