I have been running into the issue of getting the airport wifi card to properly bridge with my vmware guests. This blog post describes how to get vmware fusion 3.x working in a bridged configuration. This link here is how I was able to properly configure my macbook. You essentially add a second network adapter and assign it bridged to the (WI-FI) airport card. You may have to reboot your vm or even your wireless access point in order for it to kick in.