Note: The below solution is considering the computer you wish to connect to is turned on; has sharing enabled, has the sufficient right active and you are able to ping to it

Solution (Applies to Windows 7 / Windows 8 / Windows 8.1)

• It is most likely that this folder was accessed with a wrong password earlier
• Open Control Panel – User Accounts
• From the left panel – Click Manage your credentials

• For Windows 8 and 8.1 users the Web and Windows Credentials will show separately. Click Windows Credentials
• Under Windows Credentials; the PC name or IP Address that you were trying to connect to must be listed

• Click Remove to delete the existing credential
• Once done; try accessing the shared folder once again.