Dashlets on Dashboard displaying Not Found error
Not sure if this is solved, but we had the same issue running on a Debian server and the host was resolving the DNS name to the legacy site (we were testing). So to resolve the 404 errors on the dashlets, we had to enter a host entry in /etc/hosts to point the DNS name to the local IP address (instead of it resolving on the net to the existing legacy server IP).

If on windows, you'll need to do this in C:\Windows\System32\drivers\etc\hosts