samba - Sep 2002 - Network disks not unmounting

When I log in into the domain a logon script is started that assigns some
network drives. But when I log and on again the script gives an error in the
form of:
   The local device name is already in use
Is this a bug or is it just windows? Can anybody tell me how to solve this?

-- smb.conf --
[global]
        netbios name = BARAD-DUR
        workgroup = MIDDLE-EARTH
        server string = Middle-earth Server
        admin users = ntadmin,root

        ; Domain options
        domain master = yes
        preferred master = yes
        local master = yes
        domain admin group = ntadmin
        domain guest group = nogroup
        domain logons = yes
        security = domain
        os level = 64

        ; Password options
        smb passwd file = /usr/local/samba/private/smbpasswd
        encrypt passwords = yes
        passwd chat = *Voer oud wachtwoord in* %o\n "*Voer nieuw wachtwoord
in*" %n\n "*Voer nieuw wachtwoord in*" %n\n "*Wachtwoord
gewijzigd*"
        unix password sync = yes
        passwd program = /bin/passwd
        password level = 0
        null passwords = no
        min password length = 5
        map to guest = Never

        ; Logon options
        logon drive = h:
        logon home = \\%N\%u
        logon path = \\%N\%u
        logon script = %G\logon.bat

        ; Locking options
        lock directory = /usr/local/samba/var/locks
        lock spin count = 2
        lock spin time = 10
        locking = yes

        ; Loggin options
        log file = /usr/local/samba/var/log.%m
        log level = 3
 ; Interface options
        interfaces = eth0 192.168.1.0/24

        ; User account options
        add user script = /usr/sbin/useradd -d /dev/null -g middle-earth -s
/bin/false -M %u
        delete user script = /usr/sbin/userdel %u

        message command = /bin/mail -s 'message from %f on %m' root <
%s; rm %s

        ; Who-are-we options
        announce as = NT Server
        announce version = 4.5

        ; Filesys options
        dos filemode = no
        dos filetimes = no
        follow symlinks = yes
        force create mode = 0755
        force directory mode = 0755
        fstype = NTFS
        hide dot files = yes
        browse list = yes

        deadtime = 0
        enhanced browsing = yes

        ; Don't know options ;)
        browseable = no
        time server = yes
        socket address = 192.168.1.1

        ; Mangling options
        mangling method = hash2
        mangling char = ~

        ; NMBD options
        dns proxy = yes
        wins support = yes
        name resolve order = host lmhosts wins bcast

; Important share
[homes]
        path = /home/%U
        writeable = yes

[print$]
        path = /opt/printer
        guest ok = yes
 browseable = yes
        read only = yes
        write list = ntadmin

; Enable NT domain logons
[netlogon]
        path = /opt/netlogon
        read only = yes
        write list = ntadmin
        browseable = yes

[profiles]
        path = /home/%U
        read only = no
        create mask = 0600
        directory mask = 0700
        guest ok = no
        writeable = yes
        browseable = yes

[sysvol]
        path = /opt/sysvol
        read only = yes
        browseable = no
        write list = ntadmin

[htdocs]
        path = /var/www/htdocs
        read only = no
        guest ok = no
        valid users = ntadmin sauron maxor

[storage]
        path = /opt/storage/%G
        read only = no
        guest ok = no
        browseable = yes

[stor]
        path = /opt/storage
        read only = no
        guest ok = no
        valid users = ntadmin,sauron
        browseable = no

-- logon script --net use Y: \\barad-dur\storage
net use Z: \\barad-dur\stor
net time /set /domain:middle-earth /yes
net use lpt1: \\barad-dur\pdfprint