Thank you for your answer cheesyking,
I have checked "sudo getfacl <path to share>" - that looks OK but do you mean with "the acls in the share's setting" some special settings concerning acl in smb.conf respectively the mas-file?
I will not quote you, but thanks for that hint - I do not put the acl flag in the fstab, it was already there. It was done either by the install script of the new ebox/Zentyal or the Ubuntu10.04-Server installation.
I've also already set all processes to complain mode in apparmor, which also did not help.
Next attempt will be to deactivate the samba service in eBox and try to run it separately, because most other issues are fixed, solved and are working now.
Even if I mixed something up by chmod 777 in the share created by me, what I cannot deduce, the [homes] should behave OK. But they didn't.
Greetings