If you turned off your DHCP server follow these steps to connect to FritzBox settings.
- Set your computer IP to 169.254.1.2and your mask to255.255.0.0
- Then go to 169.254.1.1, login and re-enable the DHCP server.
On gnome turn the wired connection off on again to apply the settings.
Note: why in the hell does FritzBox 7490 require a land-line telephone to be physically factory reset?