ifconfig says yes ping says no

i am running knoppix 3.7 on two boxes and i have the same issue

i have two network interfaces eth0 and eth1
eth1 is the usb modem to internet
eth0 is network card to local network

every time i boot up i watch the screen info fly by and i can see the network interfaces being brought up and then back grounding?

when i log in and ifconfig all the interfaces are up and running (even control centre agrees) but if i ping a web address nothing happens

i have to go to netcardconfig and re set the eth1 interface (this often causes eth0 to fall out of bed so i have to restart that again)

i run a web server and this is a real pain in the but

can someone help

i am fairly ok with command line work if needed

m