problems for netsaint using sudo

[Andrea]

I'm trying to let netsaint restart services in case of problems.
I put netsaint in the sudoers file for the restart program, 
but when the event handler executes nothing happens 
(even if the auth log registers the sudo call correctly).

Do you have any clue ?
thanks

some configuration details:

/etc/sudoers
netsaint ALL=NOPASSWD:/usr/lib/netsaint/plugins/restart_service

ls -l /usr/bin/sudo
-rwsr-xr-x    1 root     root        80584 Apr 27  2002 /usr/bin/sudo

/etc/netsaint/command.cfg
command[restart-http]=sudo /usr/lib/netsaint/plugins/restart_service
$SERVICESTATE$ $STATETYPE$ $SERVICEATTEMPT$ apache

ls -l /usr/lib/netsaint/plugins/restart_service
-rwxr-xr-x    1 root     root        31829 Apr  7 18:20
/usr/lib/netsaint/plugins/restart_service

less /etc/passwd | grep netsaint
netsaint:x:103:103::/var/log/netsaint:/bin/sh

example from /var/log/auth:
Jun  9 06:42:38 astio /usr/bin/sudo: netsaint : TTY=unknown ; PWD=/ ;
USER=root ; COMMAND=/usr/lib/netsaint/plugins/restart_service CRITICAL
HARD 4 apache

-- 
Andrea Passerini