>I create a business object for invoices with 2 tables: Invoice (default) and InvoiceList. I also have a business object for stores. My form has a combo box for stores, which populates correctly. The combo box for invoices uses the table invoicelist as its binding source. It should have the invoices for all the stores at start up but it is not loading at all.

Let's tackle the problem of not loading invoices for all stores at startup. Try moving the code that retrieves stores and invoices AFTER the call to InitializeComponent. Before InitializeComponent() executes, none of your UI controls are instantiated, so you need to wait until after it executes to call methods that populate the controls.

public ViewInvoices()
{
//Get data for drop down lists
this.oStores = (Stores)this.RegisterBizObj(new Stores());
this.oInvoice = (Invoice)this.RegisterPrimaryBizObj(new Invoice());

InitializeComponent();

oStores.GetAllStores();
oInvoice.GetUniqueInvoices("*");
}

Best Regards,