Such is noted widely in newsgroups. No solution found except to have Canon fix it. Or leave the battery out.

In fact, try that! Take the battery out of the charger after a charge and see if it holds the charge overnight...

Bob

PS.http://www.photographyblog.com/comments.php?id=1549_0_1_0_C

"In the short term, the problem can be avoided by unloading then re-loading the batteries just after the camera is switched off. The camera's power supply will then perform normally."

Hey, no feedback please. Try it. Yes, I know it's not your camera, but do try these tests.