Wifi card see only old AP and not the nearest

Hello everyone,
I have 3 AP Netgear, one (the oldest) is WG302 and the others 2 are WG302B.
I had the latest 2 access point configured as repeater of the first and everything was going well.

Now I connected the 2 WG302B with a cable, but some pcs in network (with Windows XP SP2 and variuos hardware and wifi conf software) doesn't see the SSID and cannot connect, except to the central AP (the WG302 one - and the signal is very poor). The configurations in APS and in PCs are correct, in fact other clients work perfectly.

How can I force the client to connect to the nearest AP without changing the SSID? For info, the 3 AP have got 3 different channel for data transmission.

Thanks in advance