Post the result of ifconfig.

What brand and model of router is it? (yes, I'm asking this for a reason.) Are you sure that the router isn't limiting access because of some setup issue, such as a MAC address table? We have seen this in these forums before, and it seems the most likely issue from what information you have given us. I suggest going into the router setup and turning off any router feature that limits Internet access, MAC filtering, IP address filtering, time of day filtering or any other rule that you might be imposing (save your router configuration first so you can reload it if you wish). Warning: do not use the logic "this same NIC worked under Windows so I can leave the MAC address filters in place".