Hmm, probably the first thing your going to want to do is run the Connection Wizard in the PS3 and 360. If possible, try to set the PS3 with a Static DNS. You should find the DNS on the router's status page, let us know if you need details. If you just hook up a PS3 wired after its been wireless for a while, hyperthetically, it could still be running wirelessly, and thus show you no difference at all.
Other then that, yea, look at your configuration..