Networking Problem

I am having a problem networking with a wireless router and Vista and XP computers.

 

Here's what I have : Dell Dimension running XP, 2 Inspiron notebooks running Vista, 1 notebook running XP. My printer is plugged in to the Dimension. All of the laptops connect wirelessly and the Dimension is plugged in to the router. The router is a Linksys WRT64G and I have updated the firmware. None of the notebooks can communicate with the Dimension. If I look at the network map using Vista, it looks like this;

 

Inspiron  (Vista)----------WRT64G------------Internet

                                            |

                                            |

Dimension (XP)-----------Switch

 

On the network map, I can see the Dimension, but I am unable to connect to it. There is no separate switch installed. I guess they are considering the rj45 ports on the wireless router to be the switch. I called Linksys for support, but they said they don't offer networking support. Any ideas on how I can get all of these computers to communicate?

 

Thank you