I have a ubuntu server 12.04 which was connected to my wireless network with no problem

I replaced the wireless router but kept the ESSID and password the same.

All other devices on network have connected correctly.

However the Ubuntu Server will not route correctly.

It will connect to the wifi router, and get a dhcp served IP address, however it will not route anything. I cannot ping the router from the server. the contents of /etc/resolve.conf are updated with the information from the router, (the host name has been served)

I know there is nothing wrong with the router or the server, or the wireless card etc.

I'm assuming there's some cached setting that associates the old router with the ESSID and causing the issue.

I've got a lot of other devices connected to the router, so don't want to change the name of the ESSID.

How do I fix this?

EDIT: outputs (abbreviated as I've got no cut and paste)

netstat -rn:
Kernel IP Routing table
Dest        Gate        Gen            Flags     MSS Window     irtt     Iface
0.0.0.0     192.168.0.1 0.0.0.0.       UG          0 0          0        wlan0
192.168.0.0 0.0.0.0.    255.255.255.0  U           0 0          0        wlan0