Help with IE6 popups needed

[chrisp]

I have an ASP.NET 2 main web page (IE6) with a Find button which needs to
display a Find Item dialog, let the user enter search criteria, populate the
dialog it with a list of items from a database search, let the user select
an item and then return the selected item's Id back to the main web page.

I've been trying to display the Find Item dialogue as a popup using the
JavaScript showModalDialog method but I can't get it to work. The Find Item
popup is displayed but when I click on the Search button to make it query
the database then I just get a second IE window displayed which shows the
Find Dialog dialog. The second IE window is not displayed as a popup.

Can somebody help me out? I'm using IE6 with client-side JavaScript. All
database access is done server-side.