Displaying a Centered Pop-Up Window

I have been using code I recently found on Kirupa called **Displaying a Centered Pop-Up Window. **It works great and I love it! But I ran into an anoying problem.
I have this feature attached to 6 buttons that pop up windows to different URL’s. The window gets stuck on one size and completely ignores my attemps to change to a different size… like it’s locked into my first code of 600 x 300. I’ve tried re-uploading the FLV file, purging internet memory and refreshing but the window size just won’t change. Here is the link where I found the code;
http://www.kirupa.com/developer/mx/centered_popup.htm

My site is www.house-maps.com . Click on “Interesting Things” and then click on one of t he links. I am trying to get the pop up window to match the size of the URL but it ignores any attempt.

Seems so simple but it’s driving me NUTS! Thanks to anyone for advice!!

John