Replacement NV+ chassis

Ok. So I've got my replacement chassis, updated its firmware to 4.1.8, migrated the disks from my old chassis and now I've changed the security mode to User from Share as per SPHARDY's pdf. I've created some new shares and am copying the original shares to the new shares in line with his advice and will delete the original shares when this is complete. I'm hoping that this will resolve my access problems, which are as follows (bear with me please):
I try to connect under windows 7 network and see the Readnas Hostname. When I click this it asks, sometimes I get access to all the shares without any dialog, but sometimes up pops the dreaded 'Enter Network Password' dialog. Entering the user details and password to match Frontview, brings up 'Logon failure: unknown user name or bad password'. If I restart, it's pot luck whether I can connect.
I think this has all come about by upgrading to 4.1.8 and it's driving me crazy. Does anyone know whether the issue is caused by the fact that the original shares created under 'Share' Security Mode are still there or is it a Windows 7 issue?
Thanks