fckdialog custom javascript not working in IE

I've added some custom javascript to fck_image.html that displays a "file loading" kind of message. It works fine in Firefox, but it doesn't work in IE. If I go directly to the page in my browser (i.e. http://domain.com/fckeditor/editor/dial ... image.html), then the javascript works fine in IE. I wanted to make the fckdialog bigger and show all the normal IE window stuff so that I can view source and also see javascript errors in the lower-left corner of the window (you know, that yellow triangle exclamation point?). I can't figure out how to do that. I got all the way down to fckeditor/editor/_source/internals/fckdialog_ie.js and found

oReturn = parentWindow.showModalDialog(pageUrl, dialogInfo, sOptions);

I tried changing that line, but absolutely nothing happens. I can even type things like "fdas", expecting to get an error, but nothing happens. What am I missing here? Does anyone have any ideas?

Thanks!