This is perhaps not a bug, rather a functional choice. The datepicker in the EditorGrid does not seem to allow selecting today's date from the calender. You have to use the "Today" button and cannot click the date in the actual calendar itself. Also, if you try to click the value that is currently slelected (ex 1/1/2007 is the current value, you cannot click 1/1/2007 in the DatePicker)
It is easy enough to work-around, but I think it's a bit unexpected and likely to send some support calls my way until users get used to that. I think it would be nicer if those dates are also clickable, even though it is a bit redundant.