My computer wont connect to the internet when my router is plugged in, yet my wifi is still available?

Ok so here goes, my wireless router has worked all along but i went to a friends house last night and hooked it up there so we could play xbox live. I come home today and hook it up and dont really go on the computer but just keep messin around with my ipod touch, which still has wifi connectivity. When i try to go on my computer, it says there is limited or no connectivity, yet i have full wifi connectivity? The link light on my modem still flashes but the one on the wireless router doesnt, also the ethernet port lights only flash when i have my modem directly plugged into my computer, if anyone has any ideas on how to fix this, please throw them out there. P.S. even when i have my wireless router plugged into the computer, i cant search its default ip address, so anyone, please help!