samba+autofs in ubuntu

[albi]

today i've switched from debian stable to ubuntu warty on a fileserver 
(an AMD64, using ubuntu for AMD64), so far it works great, apart from
one little annoying thing, and that's permission-complaints from both
midnight commander and konqueror

the setup is like this :

autofs is installed on the clients (debian), /etc/auto.smb looks
like this (example) :

Data -fstype=smbfs,uid=myuser,gid=myuser,fmask=660,dmask=777, \
username=myuser,password=myuser ://mysambaserver/Data

the relevant part of the /etc/samba/smb.conf on the sambaserver
(the fileserver mentioned above)

[Data]
         invalid users = bg
         path = /Data
         strict locking = yes
         sync always = yes
         comment = Data
;       create mode = 2664
         force create mode = 664
;       short preserve case = yes
;       case sensitive = yes
;       directory mode = 2775
         force directory mode = 2775
;       follow symlinks = yes
         map archive = no
         map system = no
         map hidden = no
;       force user = myuser
;       force group = myuser
         inherit permissions = yes
;       force security mode = 0770

so far this all works fine with samba 3.x on ubuntu apart from one
thing, midnight commander complains with "cannot chmod target file..
Operation not permitted (1)"

konqueror complains with a similar error (can't try it now from here)
and cp -axvr complains with :
cp: preserving times for `some_file.txt': Operation not permitted
(with debian-stable this used to work without any problems)

the copying-result is fine and how i'd like it to be, but i'd like to 
get rid of the error-messages, any ideas ? thnx!