"Lock Session" freezes computer

[Guest]

I have a Lenovo T60 Thinkpad and am running Kubuntu 8.04. I recently started having problems with the "Lock Session" feature. When I select it the laptop freezes and I can only do a power button reboot. I didn't notice the problem before I started using fglrx in dual-head mode and suspect that is the problem. I ran the following command to enable dual-head:

aticonfig --initial=dual-head --screen-layout=left

And here is my system information:

Linux kubuntu-scottw 2.6.24-21-generic #1 SMP Tue Aug 12 13:37:22 UTC 2008 i686 GNU/Linux

Distributor ID: Ubuntu
Description: Ubuntu 8.04.1
Release: 8.04
Codename: hardy

Any thoughts? Thanks.