Same problem here, but I found what causes this problem!
I have a system user A, created with useradd and also user with same name A in eBox. When I check user A from console:
$ id A
uid=1000(A) gid=1000(A) groups=1000(A),4(adm),20(dialout),24(cdrom),46(plugdev),109(sambashare),113(lpadmin),114(admin),513(Domain Users)
Also there is user B created only from eBox:
$ id A
uid=2023(B) gid=1901(__USERS__) groups=1901(__USERS__),513(Domain Users)
New shared folder has these rights:
$ drw-rw--- 2 ebox __USERS__ 4096 2010-07-28 15:31 /home/samba/shares/boo
Both users (A and B) in eBox have same rights, but only B user can access boo share, because he has correct groups created by eBox.
So the problem is with system users. Don't know how to fix it and how to add an LDAP group tu system user?