^^try looking at the documentation that came with the router. You could also try "admin" for the username and " " (~empty~) for the password as that is a common default for older routers; though most newer routers have a random alphanumeric password for the default (e.g."00s76a54fr675") So yeah, the defaults should be listed in the documentation.
Also, and I don't know if this could be the problem, but I had a similar problem with hooking more than two computers to a router at once and it turned out the router was messed up. If you can't get it it to work any other way, I would recommend purchasing a new router. A decent combo wireless/wired router (wired for your desktop(s) and wireless for your PS3/laptop) only costs like $70 or so.
Also, if anyone ever tells you that wireless is too slow for gaming, it's not true. Wireless G routers, which are the virtual industry standard, have a maximum data tranfer rate of 54mbits/s. The fastest internet connection I have ever even seen advertised is the Premium Verizon FIOS package @ 30mbits/s, which is only 56% of Wireless G's max rate. (and that package costs $140/month!!)
Not trying to be a fanboy. Of course, it's hard when you own the best console eve... dang it
