Are you tagging VLANs from your 2930M core switch to the IAPs?
The IAP cluster will treat wireless users in one of two ways. It will either connect users to a wired VLAN, or it can place users on an internal VLAN and then NAT the wireless traffic out to the wired network using the Virtual Controller's IP address.
When you configured the SSID on the IAP, did you select the Client VLAN assignment as default, static, or dynamic?