Is this network switch borked or crud?

My GF's BB connection supplies her with a BT Voyager modem/router, which has a USB port and a LAN port, which can be both used at the same time. From this LAN port, a Belkin network switch is attached to supply the rest of the house with BB.

Here's the problem:

When I'm over in her place, I connect to the net on my Powerbook via the network switch, on which I get some of work done and play WoW. This is all fine UNTIL someone else connects to the net via the switch as well. It could be something as simple as MSN, but once this happens, all connections off the switch hangs. Closing all apps on all PCs doesn't help, and the only way to get the switch functioning again is to press the 'reset' switch on the back.

Is there something I could do to fix this? Or is the switch crud?