Kudzu/RTL8139.cs
var xEthernet = new Cosmos.Sys.Network.EthernetPacket(xUDP.GetData()
//, 0x525400123457
//, 0xFFFFFFFFFFFF
, 0x800);
Go to the constructor declaration and change it to include the MAC ID's which are UInt64's.
Now uncomment those 2 lines and run, and it crashes at run time with a GPF.