> ktrace didn't find the mount command.
> Do you have /sbin in your path ?
> How did you start the command ?

I have /sbin in my path. I have invoked the command as:

mount export:/mnt /mnt
mount -t nfs export:/mnt /mnt
mount_nfs export:/mnt /mnt

from /sbin as:

./mount export:/mnt /mnt
./mount -t nfs export:/mnt /mnt
./mount_nfs export:/mnt /mnt

I get "Operation not supported by device" for each form. ktrace produces the
same results on each form. To the best of my knoweledge, the kernels are all
current and configured properly and all necessary software is running on both
the client and the server. This is most curious to me.