After reading some of the posts on the OPML Newbies Yahoo Groups page, it turns out that the OPML Editor doesn’t like IE 7. After hunting around the Add/Remove Programs I managed to find the IE 7 entry and uninstalled it.
The only problem is that i’m a web developer/designer and would like to have IE 7 to test new sites on. So i did a search and found a way to have IE 7 run as a standalone app.