Have you tried populating your combobox from a dataset
using the following properties...
cbo1.DisplayMember = "UserTypeDesc"
cbo1.ValueMember = "UserTypeId"
and then set:
cbo1.SelectedValue = User.UserTypeId
The above reference is a 'User' Object with the Property 'UserTypeId'
Seems to get the same results without creating additional classes and uses the inherent object properties