samba - Dec 2012 - user can't access subdirectories on share using Win7

Hello,
I have samba 3.5.6  PDC and BDC on debian squeeze with openldap backend 
and couple samba member servers based on samba 3.5.15 and 3.6.6 on 
solaris 11 delivering shares to windows and linux users.

recently we moved from samba 3.0.24 on solaris to  above verions and we 
stuck with a problem on windows 7 machines.

on solaris zfs filsystem mounted with these settings:
drwxrws--t  20 root     dnateam       22 Dec  7 11:48 sample_tracking

and exported with samba:
[sample_tracking]
         path = /dataPool/samples/sample_tracking
         force group = dnateam
         force create mode = 0770
         force directory mode = 0770
         browsable = yes
         read only = yes
         veto oplock files = /*.mdb/*.MDB/
         write list = @"DIL_\informatics"
         valid users = @"DIL_\dnateam" @"DIL_\informatics"

in sample tracking directory there are subdirectories  with  files and 
projects ex.
drwxrws---  59 mattw    informatics      61 Dec 14 17:37 projects

When I mount this share on windows XP or servr 2003 on my account

groups wojciech
informatics  sample_management dnateam sampleinf

I have access to sample tracking projects and all subdirectories but 
when I mount it on Win7 or server 2008 have an access to sample tracking 
(can create files directories) but can't enter projects directory. 
(access denied). when i add o+rx on projects problem moves one level 
deeper.

I was checking logs while I try accessing projects no information 
appeared in logs (not event connections). logleve is 5.  it looks like 
windows 7 gives access denied without connection to samba server. What 
might be a problem? win 7 security setting ?

Win7 has all these setting:
Network security: LAN Manager authentication level
  Send LM & NTLM responses

Minimum session security for NTLM SSP
  Disable Require 128-bit encryption

thanks
Wojciech