no internet connection

[philipp sutter]

hi, i just installed ubunte 5.10 on two computers. one is a laptop. on
both i do not get an internet connection. the strange thing is that the
laptop can establish a connection in my office where i have an other
isp. but when i connect the laptop at home i dont get a connection (no
ip, no dns; nore when i use fixed ip). the pc and the laptop uses at
home the same isp (chello.at). 
has anybody an idea how to solve this problem. thanks for any hint.