Network Support Thoughts Please

I've changed my network configuration to take the WiFi Router out of the main branches because it seemed to fall over a lot.

So now I have:

DOWNSTAIRS:
WiFi Router connected only to the Switch
Switch connected to MAIN PC and POWERLINE HUB 1

POWERLINE HUB2 - Connected to Network Printer

UPSTAIRS:
POWERLINE HUB 3 - Connected to Switch 2
Switch 2:
 > DSL Modem
 > Media Center PC
 > Network HDD

All seems to be working BUT...

The laptops can't see the home network.  They can see the internet and the network printer but can't seem to access any of the shared network resources.

If I plug a Cat5 cable into the laptop suddenly it all works and can see everything and access everything so the permissions seem to be set right.  But why can't I access the network over WiFi.

All stuff is XP except the laptop which is Vista.

Thoughts?

Oh, and the throughput on the Powerline Network is Bloody Awful but that must be a problem with my wiring.