Wifi fine but wont connect new device

I dont know if any of you will be able to help me but im running out of ideas.

For some reason i cant connect any new devices to my wifi. My laptop and ipod are working fine and are happily connected to the network. Its only when i try to connect another device like my other desktop or psp that it tells me that it has limited connectibility, even though it has full signal strength.

Im confused with this one as its actually working for computers that had previously been connected to it.

Conorp

There may be a setting in its configuration to limit the number of connections. Or perhaps the security settings aren't as you remember.
Whenever I have difficulty connecting a device, I turn off my security (including mac filtering!) and connect that way first, to make sure everything is functioning. Then I turn my security back on a step at a time.
It could be something simple. Is it set for b/g mix? if not and your pc's only have 802.11b cards, they may not work.
Also check the settings on the pc cards. Make sure under tcp/ip properties they are set to obtain internet address via DHCP.