Running 5.0.9 NE and I have a mailbox that once you enter the Preferences->Mail tab on FF3 or IE7 (only ones I've tested) you cannot save or exit without saving changes. I think it has something to do with the Out-of-Office messages, but when I look at the account with the CLI I don't see anything too wonky.
The UI throws up it's red error box that fades in and out which reads "A required value is missing or invalid".
Ideas? Known bug? The Error console in FF shows this._startDateCheckbox is undefinded and this._endDateCheckbox is undefined when you click on the checkboxes above the Start and End date for enabled / disabling the OOM.