I have read a few posts where users test a Linksys LNE100TX NIC and they get a address of FFFFFFFFFFFF. I recently bought one of their network in a box kits w/ those cards and I noticed the same thing.
First off, here is the system I am trying to install the card in.
FIC VA503+ motherboard w/ VIA chipset
AMD K6-2 350MHz CPU
128 MB RAM
Here are my observations. If I run Linksys' diagnostic program (runs in DOS) just after physically installing the card but before Windows has detected and installed the drivers, I get a valid MAC address. However, after Windows has installed the drivers, the MAC address becomes FFFFFFFFFFFF. This happens every time I physically take the card out and replace it. I have tried it on both cards with the same result.
Also, the network does work using Netbios or TCPIP. However, I need to be able to use IPX for some of my games. Whenever I run Net Diag in Windows, I get "Unable to open IPX socket".
I do not know if one problem is related to the other or if they are 2 different issues. Any advice would be appreciated.