I wonder whether it may have to do with your IP addresses. Are the clients looking for "server" or 192.168.0.2? Perhaps with the change in the router the new IP address is 192.168.0.8 and they are not finding the correct information.
Another possibility is the permissions. With a new system could come a new network. Make sure the network is considered to be private or work. recheck the sharing permissions on the AC folder as well as the permissions on the AC databases(R click/properties, "everyone" should be in with full control in permissions.)
If you're not comfortable with this, perhaps call AC help
