Cannot ping outside university

[David]

About fie weeks ago I installed Dapper on a Dell Inspiron 6000
laptop. Everything was going great, I configured the eth0 interface to
get onto the university network and I could connect to Ubuntu
repositories and I downloaded various software eg. GRASS, R etc.

Then some days later I lost the internet connection. I do not know
why. I can still ping my PC and the PC can still ping the laptop. But
the laptop cannot ping websites or repos.

To make matters worse, we need this sorted within the next 24 hours!
Any help would be greatly appreciated.

dave