After wake from sleep, I get the message "Please connect..." and the pad is unresponsive.
If I then re-install the Mac driver, the quick keys becomes responsive.
Are you using the Xencelabs Quick Keys or the Pen Tablet? How is the Xencelabs device connected to your Mac? Are you using a USB hub, and is it powered (it has a wall power) or passive (no wall power)?
If you turn your Xencelabs device Off and then back on. Does this help?