If you're using Active Directory, please make sure you are running the Ninite .exe itself as a domain administrator instead of passing the credentials to Ninite.
In order to run Ninite remotely, the following settings must be set on the remote computer:
If Ninite can't connect, you can run the following .exe on the remote computer to set these correctly: EnableRemote.exe
Also, the remote computer has to be accessed through an administrator account that has a password set (it won't work with an empty password).
According to Microsoft TCP ports 139 and 445 and UDP ports 137 and 138 should be accessible for Ninite remote to function.
If you get an error "Failed - Not enough server storage is available to process the command. 8107" you can fix it by increasing the IRPStackSize value.