cannot connect to router....help

my imac is connected by ethernet to router and works fine, however, when i remove the ethernet and try to connect wirelessly i have no joy no matter what i do. incidently i have a pc upstairs running windows which connects fine???

Can you tell us a bit more. What Mac is this and version of OSX? What brand and model is the router. What security are you using on the Wifi of the router? WPA? WEP? None?

24inch ally imac
belkin f5d8233 ver3
using wpa-wpa2 psk tkip+aes

also my psp and nintendo wii both connect with these settings only the imac will not

MacBook Pro on wireless network, cannot connect to internet

Need help first understanding why if I have a good wireless connection I cannot access the internet.

Specifics: MacBook Pro running 10.5.5 (just returned from Apple with new harddrive and screen) trying to access Linksys router with no security. Time Warner Cable is our ISP. We've tried every conceivable configuration. In the past I've always been able to assign a static IP and it's worked perfectly fine. Not this time! My HP PC is accessing the internet without issue. Frustrating... Any help appreciated! [This is my first post on mac-forums so hope I'm jumping on correctly ]