There is a limitation within Windows where it can only pass 1 username per device. So, if you are running in a mixed environment with both restricted and unrestricted shares you would need to map the restricted ones first. Do the following and see if it clears up the issue you are experiencing:
1) Disconnect any mapped network drives that currently exist on your computer
2) Log off and back into Windows to clear the authentication session
3) Map to your access restricted shares first
4) Map to your unrestricted shares
This should clear up your issue.