NIC problems with ASUS CUBX E

I have 53 ASUS CUBX E motherboards and have tried installing NICs in them under Linux Mandrake 6.5 & 7.1, Red Hat 6.2. We have also tried various NIC cards (all on the compatiability list) I have checked ASUS site for information but am getting nowhere. Other than getting rid of the 53 boards any ideas???