DropDownList DataBind() Error

[juts]

The following code is causing the error
"System.ArgumentOutOfRangeException: Specified argument was out of the
range of valid values. Parameter name: value" on DataBind(). The
stored procedure returns a UniqueIdentifier (the DataValueField) and a
Varchar(20). Any help anyone could provide would be greatly
appreciated!

Dim conn As New SqlConnection(Utility.ConnectionString)
Dim cmd As New SqlCommand("spOccupancyClass")
Dim dt As New DataTable

conn.Open()

cmd.Connection = conn
cmd.CommandType = CommandType.StoredProcedure

Dim da As New SqlDataAdapter(cmd)

da.Fill(dt)

With cbOccupancyClass
.DataTextField = "Description"
.DataValueField = "OccupancyClassId"
.DataSource = dt
.DataBind()
End With