There seems to be a small bug with the repeater controls.
If you don't have a data source on your ASPX page and you don't assign one to the controls on the server side, they throw an "Object reference not set to an instance of an object" exception in the CreateChildControls method.
I'm pretty sure this can be fixed just by surrounding the foreach in the middle with an "if (dataSource != null)", like so:
if (dataSource != null)
{
foreach (object o in dataSource)
{
/* details omitted */
}
}