Very Computer

I have a strange behaviour of nfs-mounts in Linux from Scratch 6.5.

My /etc/fstab has the following entry:
---- cut ----
smartass:/data/ftp/vdr      /mnt/vdr     nfs     _netdev,rw               0
0
---- cut ----

When trying to mount it by using this command "mount -avt nfs", lfs says:

mount.nfs: timeout set for Sat Dec 19 11:16:24 2009
mount.nfs: text-based options: 'addr=192.168.70.10'
mount.nfs: trying 192.168.70.10 prog 100003 vers 3 prot UDP port 2049
mount.nfs: trying 192.168.70.10 prog 100005 vers 3 prot UDP port 32770
mount.nfs: text-based options (retry):
'addr=192.168.70.10,nfsvers=3,proto=udp'
smartass:/data/ftp/vdr on /mnt/vdr type nfs (rw,_netdev)
nothing was mounted

When unmounting it, it does it only once; "umount -avt nfs":

umount.nfs: trying 192.168.70.10 prog 100005 vers 3 prot UDP port 32770
smartass:/data/ftp/vdr umounted

Indeed the mount point was mounted actually but I don't understand why lfs
did it 2 times but umounted only one mount.
My server logged:

Dec 19 11:24:53 smartass mountd[4834]: authenticated mount request from
192.168.70.106:811 for /data/ftp/vdr (/data/ftp/vdr)
Dec 19 11:24:53 smartass mountd[4834]: authenticated mount request from
192.168.70.106:909 for /data/ftp/vdr (/data/ftp/vdr)
Dec 19 11:28:25 smartass mountd[4834]: authenticated unmount request from
192.168.70.106:951 for /data/ftp/vdr (/data/ftp/vdr)

Can anybody explain that behaviour to me and help me out to solve it?

TIA!

Joe