If you had a share mounted as a Windows user (User A) and have switched to another Windows account (User B) and are then unable to mount that share again, the following steps should allow you to reconnect properly:
1. Click on the Start menu in Windows, then click "Run" and type "CMD" (+ Enter) to open a Command Prompt
2. Type "net use \\IP /d" without quotations. IP should be replaced with the IP address or host name of the NAS in question. Example: "net use 192.168.1.100 /d" or "net use NetworkSpace2 /d" (and hit Enter)
3. You may now close the command prompt and attempt to map or connect to the share.
Reason: Windows only allows one user to be authenticated to a NAS location and occasionally Windows Caching might not release an account after it has logged out. The steps above should force Windows to release "User A" from any connected shares, allowing "User B" to connect properly.