problems for automounting in squeeze

In my network I've two maschines with lenny installed. The automounter
is working in both directions. Now I added a new maschine (amd64) and I
installed squeeze. On that maschine automounting does not work. A
manual mount is no problem. Can anybody help?

More details:
server:/etc/exports
/data 192.168.1.0/24(rw,sync,no_root_squash,no_subtree_check)


client lenny:/etc/auto.master
/mnt /etc/auto.lenny --timeout=60

client lenny:/etc/auto.lenny
* -fstype=nfs,hard,intr,nodev server:/&

automount -V
Linux automount version 4.1.4_beta2


client squeeze:/etc/auto.master
/mnt /etc/auto.nfs --timeout=60

client squeeze:/etc/auto.nfs
* -fstype=nfs,hard,intr,nodev server:/&
* -fstype=nfs,hard,intr,nodev lenny:/&


automount -V
Linux automount version 5.0.4

Directories:
config dir: /etc/default
maps dir: /etc
modules dir: /usr/lib/autofs

Compile options:
ENABLE_FORCED_SHUTDOWN ENABLE_IGNORE_BUSY_MOUNTS WITH_HESIOD
WITH_LDAP WITH_SASL LIBXML2_WORKAROUND






The following command on lenny is succesful
ls -a /mnt/data
. ..

But the same command on squeeze leads to an error:
ls -a /mnt/data
ls: cannot access /mnt/data: No such file or directory

A manual mount on squeeze is succesful:
mount -tnfs server:/data /mnt
ls -a /mnt
. ..
umount /mnt

Any suggestions where to solve the problem.

Thanks
Michael