Canon has released a user-installable firmware update for the Canon EOS D30 that corrects an instance of the camera locking up, subsequent to a particular sequence of steps being performed with the camera before turning it off.
D30 firmware update screen
appears when camera detects
firmware update file on CF card
Specifically, the camera will freeze if the MENU button is pressed, then the INFO button, then the camera's power switch is then set to OFF. Switching the camera to ON at this point has no effect, and only removing the BP-511 batteries from the D30 restores proper function.
Canon's web site includes a detailed page of instructions for installing the v1.01 update; follow the "I agree and download" link at the end of the page to locate both the Mac and Windows versions of the updater, as well as a PDF version of the installation info.