ASP How to use dropdown list with objectdatasource

[MobiBob]

It must be new a newbe, freshmens error:
Please help, I will try to keep the question short:

1. I am new to ASP and I can not get this to work:

2. I am Using a
<aspropDownList in a <InsertItemTemplate> in a <asp:ListView

3. The dropdownlist during insert does not get polulated (it is empty) while the same construction and same datasource works in the edittemplate:
<aspropDownList in a <EditTemplate> in a <asp:ListView

4. I noticed that filling the dropdownlist with a <asp:ListItem works; the insert list is populated. (not usable for me)

In both cases I use the same datasource from the code behind like this :
Edit:
<aspropDownList ID="DropDownStartday" runat="server" SelectedValue='<%# Bind("startday") %>'
DataSource="<%# GetDataSourceStartDay() %>" DataValueField="daynum" DataTextField="dayname"

Insert: (with or without Selectedvalue: NoJoy)
<aspropDownList ID="DropDownStartday" runat="server"
DataSource="<%# GetDataSourceStartDay() %>" DataValueField="daynum" DataTextField="dayname"

Why does the Drowdown contains data in the editmode and not in the insertmode?

Please help, Thanks