You need to give us a clue before we can start helping you!

Does skype (on N900) work?
On your N900 are you getting the IP automatically? getting the DNS automatically?

In an X Terminal do "ping 8.8.8.8", if you don't see any obvious errors do CTRL-C then do "ping www.google.com", if you get an error saying something like unable to resolve host then it's 99.99999% certain it's a DNS problem.