Apparently the random file system failure on megatron was unrelated to the RFM card (or at least unrelated to the physical card itself, its possible I did something while installing it, however unlikely).
We installed a new hard drive, with a duplicate copy of RTL and assorted code stolen from another computer. We still need to get the host name and a variety of little details straightened out, but it boots and can talk to the internet. For the moment though, megatron thinks its name is scipe11.
You still use ssh megatron.martian to log in though.
We installed the RFM card again, and saw the exact same error as before. "NMI EVENT!" and "System halted due to fatal NMI".
Alex has hypothesized that the interface card the actual RFM card plugs into, and which provides the PCI-X connection might be the wrong type, so he has gone back to Wilson house to look for a new interface card. If that doesn't work out, we'll need to acquire a new RFM card at some point
After removing the RFM card, megatron booted up fine, and had no file system errors. So the previous failure was in fact coincidence.