SquirelandMoose reminded me of an old trick that I used to solve this type of issue....

If you have an old modem card in the computer.....install it in the furtherest slot away from the CPU (or just remove it and leave it out)

Install the NIC card in the closest available slot closest to the CPU....the video card if it is PCI can be moved to any other available slot.....If AGP then there is no need.

The two communication devices always seemed to get in the way of eaxh other and caused the conflict...