3G iPod Touch "Invalid Argument"

Whenever I turn the touch on, it appears to connect to WiFi fine (the check mark comes up with an I.P. address in the settings). But when I try to go to the appstore or Safari, I get a message saying "Operation could not be performed: Invalid Argument". Why is this? I've looked on google but I can't seem to find somewhere with an answer that works for me. I have tried resetting the general settings on the touch, 'forgetting' and reconnecting to the network, and renewing the network's lease. Thank you for any help.