BT Home Hub - More than 2 wired computers?

I have just upgraded to BT Total Broadband and installed the Home Hub which only has 2 etherenet ports. As I have 3 wired ethernet devices (2 PC's, Linksys WAP54g) I connect a 4 port switch to one of the Home Hub Ethernet ports to gain the extra connections needed. Problem is the PC connected via the switch to the Home Hub loses its internet connection after an hour or so, the cabling is fine but attempts to repair the IP address via DHCP from windows XP dont work. Powering off the Home Hub and restarting seems to cure the problem for an hour or so. The switch is new and I have tried a substitute. The network was fine with my old adsl modem router (which had 4 ports)

Can I use a switch in this way? Or will I need a router to gain the extra etherenet ports - I assume the Home Hub is a router.

Will the static IP address asigned to the WAP54g affect anything? It falls within the Home Hub's DHCP pool.

I am just trying a direct connection to the Home Hub's second ethernet port to the computer in my garden office to see whether the same problem occurs.