Did you restart NFSD after changing exports file. Not sure if it changes anything, but I've never used trailing slash myself. /usr/mount/350gb maybe?
Snippet from my rc.conf
Code:
rpcbind_enable="YES"
nfs_server_enable="YES"
nfs_server_flags="-t -n 6 -h 192.168.2.254"
mountd_flags="-r"
rpc_lockd_enable="YES"
rpc_statd_enable="YES"
and my exports.
Code:
/usr/local/www -network 192.168.2.0 -mask 255.255.255.0
/usr/local/portage -maproot=root -network 192.168.2.0 -mask 255.255.255.0