I have a online survey running in Silverlight. Out of more than 1000 onetime users, there are three users than cannot open a combobox on the first page. The control seems disabled and don't react on mouseclick. Since it is one-time user, they don't wan't to help me with debugging and I cannot reproduce the problem myself. Any ideas why 1000 users have no problem, and 3 are experiencing all controls like they were disabled?