When you have do not see your default gateway you cannot connect. This is probably because your network is down. Use a browser and enter
http://192.160.0.1 you should get the setup of your router -assuming you enter your username and password- and if you don't have to, shame.
This is assuming you have the router on the same address check the settings in your manual if you are unfamiliar.
You should find under adsl or ppp or config a line saying disconnected click on the change button on this page and it should reconnect after 20 secs approx.
(Most use the connexant wireless router chipset described here, or something similar.)
You will now have to reboot your laptop to get the dns entries from your ip etc.
The problem if this sorts everything is that your ip provider is dropping your connection and is not hot wiring the connections. Some ip providers
if they do maintenance drop all connections and your router has to re logon, other ip's do hot wiring remembering the connections and reconnect after maintenance.
I get round this with rebooting my router. If your on holiday -and you need to connect to your machine, or hosting websites- this is solved by having a timer
disconnecting once a day to at least ensure reconnection with the ip.