networking issues on dapper

[Max Andersen]

Hi,

I have an IBM Thinkpad T42p with ubunut dapper.

My dapper has been acting strange on my home network. I connect 
wirelessly to an access point (3 windows machines (the kids) works fine. 
I get my dhcp-address, get the broadcasted dns-server and can connect to 
the inernal mailserver, etc., but cannot get routed to the internet. 
Everything I try to contact externally gets a timeout.

When using ethereal to analyze packets, i get some strange noise like 
[TCP ACKed lost segment].

my eth0 (cable) has the same issues, but works fine at work. It's only 
at home (wireless and cable) it doesn't work.

Anyone seen this behaviour before?

Sincerely
Max Andersen