How do you map shared drive in Win7 Pro?, is it like followings:
1- right-click on "My Computer" > "Map network drive..."
2- \\yourNAS-IPaddress\yoursharedfolder
3- Enter your NAS username/password?
Step 3, you need to enter your NAS web-admin user name and password, not the one you set for your shared folder.
If you still cannot access, please try to disable any antivirus/antispyware that you may have running on your desktop, just to be sure that nothing obscures your connection. If you can access after disable these software, then these software is to blame.