Access network with windows 7

To summarise, I am connecting to the network with a windows 7 laptop via a secure wireless WPA-PSK (TKIP) and I am unable to open folders on the ubuntu machine but folders on a Windows XP machine can be opened
When I use an unsecure wireless connection to the Win 7 machine via a powerline wireless range extender I get full access.
When I connect an ethernet cable via powerline and close the wireless link I again get full access.

I am connected to a Thomson Speedtouch ST585v6s1 wireless router

Ubuntu 10.04 LTS Desktop edition installed
I expected to connect to files and printer on the Ubuntu machine via the secure wireless link on the windows 7 laptop
but I was unable to connect

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: smbclient 2:3.4.7~dfsg-1ubuntu3.8
ProcVersionSignature: Ubuntu 2.6.32-37.81-generic 2.6.32.49+drm33.21
Uname: Linux 2.6.32-37-generic i686
Architecture: i386
Date: Sat Jan 21 16:48:22 2012
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release i386 (20100429)
ProcEnviron:
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SambaServerRegression: No
SourcePackage: samba
WindowsFailedConnect: Yes