Try running portmap in debug mode: kill it, and let root run it in a tty
with the flags -d -v. It should be a bit more verbose about what is happening.
Alternatively, considering the source code of the portmap used in the RedHat
distribution (and I suppose it is used elsewhere also), it is not surprising
that it crashes... on my alpha box, it produced some segmentation faults...
so I began to write my own portmap. It is not finished yet, but already
functionnal enough to handle nfs.
Send me a mail if you want the source code.
--Thomas Pornin