"Event Date" changes when "Except date" falls on one of the one of the event dates

I've run into a problem with the date of a repeating event changing when an "Except date" falls on the same day as one of the recurring dates.

For example, if I set an event to repeat every week beginning with Dec 6, 2008 and I set an "except" for Dec 27, 2008, the entire event gets saved to Dec 7, 2008 with all weekly repetitions changing similarly.

Am I setting something up incorrectly?