Consider updating your /etc/resolv.conf file to tell you wrt where the DNS servers are.
Do it by typing :
rm /etc/resolv.conf
cp /rom/etc/resolv.conf /etc
vi /etc/resolv.conf
And add something like :
nameserver 192.168.0.1
nameserver 192.168.0.2
Where the addresses are your provider's ones. Then ensure your router has a route to the internet :
route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
default longchamp44-1-8 0.0.0.0 UG 0 0 0 vlan1
If there is not any, then try :
route add default gw <provide router>
If you still think of get back to linksys firmwares then activate the boot wait and download a tftp client :
nvram set boot_wait=on
nvram commit
reboot
Then you will have to tftp you router (via command line or graphical interface), activate the binary transmission and send the firmware, eg :
tftp <router IP address>
tftp> binary
tftp> rexmt 1
tftp> trace
Packet tracing on.
tftp> put <linksys-firmware-name.bin>
Good luck !