Remove CF card and write RAIDiator 4.1.8 (http://www.readynas.com/RAIDiator_4_1_8_Notes
) to the CF card using rawrite. I think it's either that or NTRawrite depending on what version of Windows you use.
Then put CF card back in NAS and see if you still have the same problem. If you still have a problem you could try an older firmware, and if that doesn't work try replacing with CF card 128MB or greater in capacity. The CF cards have been known to fail very rarely but your NAS is quite old now.