Welcome to the MacNN Forums! But you'll have to give us a lot more information about what you're trying and what actually happens before we can help you. For example, is your wireless connection through an AirPort Base Station? What kind of security protocol are you using?
If you scan this forum, you'll see that a lot of people are having this issue, so there is obviously something going on with Intel-based Macs and AirPort. But you may simply have a setting issue-and we can't tell if you don't tell us what your settings are.