If you have an ASP.NET page (.aspx) opened with the JavaScript showModalDialog() function and inside that page there is a form doing PostBack, when the PostBack is being done the page loads in another (popup) window. The easiest way to prevent this is to add the following tag inside the <HEAD></HEAD> tags of the ASP.NET page:
| <base target=”_self”> |
Chris May 
That’s embarassing. I ran into this issue a few years back and, as I recall, worked around it by relaying the page through an iFrame – and that got baked into a library I’ve been using since. That works, of course, but it’s a bit kludgy compared to this simple work around. Thanks for posting.