Hello,
what kind of kernel and what vzctl version do you have?
Where have you downloaded your debian-4.0-i386-minimal template?
I tried to set up the same configuration but couldn't get this error message.
# vzctl --version
vzctl version 3.0.23
# uname -r
2.6.18-92.1.13.el5.028stab059.6PAE
# mount
...
$IP_ADDR:/media/ubuntu/vz/ on /var/lib/vz type nfs (rw,sync,hard,intr,addr=$IP_ADDR)
# grep -i ostemplate /etc/vz/conf/101.conf
OSTEMPLATE="debian-4.0-i386-minimal"
# ls -l /vz
lrwxrwxrwx 1 root root 11 Jan 12 14:59 /vz -> /var/lib/vz
# vzctl enter 101
entered into CT 101
# df -h
Filesystem Size Used Avail Use% Mounted on
simfs 1.0G 151M 873M 15% /
tmpfs 252M 0 252M 0% /lib/init/rw
tmpfs 252M 0 252M 0% /dev/shm