Connecting PC and Xbox via wireless network

Hi,

My son recently got an Xbox360 and is trying to get it connected to our PC's
on our wireless network at home in order to play multiplayer games

The Xbox is able to access the internet and the Xbox Live servers but cannot
see or communicate with the PC's that are on the same network....

We are connected to the internet via a static IP wireless broadband through
a GNET IP0004 router and an GWL 2100 wireless access point

We have 4 PC's running on the wireless network along with a networked printer

The router has issued unique IP addresses for each device including the Xbox
and the MAC for the Xbox shows in the client list of the router

Windows Media Player 11 sees the Xbox in the Media Sharing dialog but cannot
access the Xbox and vice-versa

Ping to the xbox from the PC fails

There are no antivirus / firewall / internet protection services running at
present and all specified ports are available to the xbox

am I missing something? aren't Xboxes supposed to act just like a PC on the
network?

I tried using the windows connect now but it wants to set up an encrypted
password which would freeze out the other devices including the printer from
accessing the network

any xbox networking gurus out there? the Xbox support service can't get
it's head around the fact that I am trying to communicate from Xbox to PC,
not Xbox to internet (which works okay)

thanks!

--
Mike Marini
Port Dover Ontario
Canada