Cannot decrypt WPA2 despite EAPOL capture

Hello everyone,

I have spent several hours trying to get this to work without any success, so I would really appreciate your help. So here is the scenario, I have a Macbook pro running Mac OS X Lion connected to my home wireless network secured with WPA2. I have Wireshark running on this computer and want to capture and decrypt the traffic. I have specified the passphrase and the network SSID in IEEE 802.11 from the protocols list under Edit-> Preferences. I have also done it in the Wireless toolbar.

Now when I start the capture, I can decrypt the traffic to and from Macook pro running Wireshark but not from another computer connected to the same wireless network even if I disconnect and re-associate that computer with the wireless network. I can see the 4-way EAPOL handshake from that computer in my trace but the traffic following that is not decrypted.

Any ideas what I might be doing wrong here please?