When disabling a raddatetimepicker the width will change from its preset width to a much larger width when you hover over it. Putting the following code and viewing it in ie9 will show the issue.
I am using 2012.1.411
I am using 2012.1.411
<Rad:RadDateTimePicker ID="RadDatePicker1" Enabled="false" Width="170" runat="server"></Rad:RadDateTimePicker>