This Forum Beta is ONLY for registered owners of D-Link products in the USA for which we have created boards at this time.
First question, did you set up your new router exactly the same as your old one?If something was working and now isn't and you have changed a component in the chain then the first place to look to start solving the problem is the changed component.
Have you changed everything on your network from the 192.168.100.xxx subnet to the 192.168.0.xxx subnet?Those getting an IP address via DHCP will do so automatically but anything you hard wired the old address into will require that you manually change it.
Then the thing to look for is how you accessed the NAS before, in other words did you access it by name or IP?If it was by IP then have you changed that old IP to the new one?