Portmap was originally set to look at 127.0.0.1. I changed it to the eth0 address, and the problem remained. nis at this point was also not working, rpcinfo -p was not giving out info, unless you either specified loopback, or the hostname. Changed portmap to listen to both sides, nis started working, and so has nfs, the computer hasn't crashed since.

Thanks for your help!