>Now.  Nothing happens.  If I do infact switch to the netboot.sunos program that
>comes with Xkernel, it loads the kernel (the NetBSD one) and then crashes out

Comments here have indicated that there was a problem with earlier
versions of netbsd netboot; make sure you have the latest, I'm told it
has some changes to make it handle this in a more robust manner.

(as for the RPC timeout, that might mean you don't have a bootparamd
running... bootparamd is not the same as bootpd... )