SIOCADDRT: Files Exists when Linux Firewall is up

[Darren_85]

I'm hoping there are some routing experts out there that can help me. I'm using Mandrake 9.0 and iptables as my firewall. previously I'm runnig an ADSL service with fixed IP. The problem happen when I upgrade to SDSL and change the IP that provide by ISP. When I trying up the firewall, Its stopping and starting the kernel with all OK. After the firewall is up, Its prompt a message SIOCADDRT: Files Exists. I knew that it was a duplicate routing exists. But its seem working fine when I using ADSL services. And after the firewall up its continues prompt up a debug message, its not suppose prompt up any message. The message is saying all the packet drop. And I even can't ping to gateway and nslookup as well. I have try to using my laptop for testing, its working fine.

TIA!
Darren