I didn't notice any mention of which version of IE anyone is using. Maybe it's not working with 6, and so not working for some visitors that you don't know about.
Thanks for this contribution. I found this topic while searching for a solution to spaces in usernames, so I really appreciate your efforts. I'm using IE7 and the latest FF, so will have to find someone using an older IE so I can test it. I'm guessing as much as 10% of my sites visitors may still be using IE6, and since I'm implementing the userpages hack (
www.joomlapolis.com/component/option,com_joomlaboard/Itemid,38/func,view/catid,19/id,15382/) this may be a real issue.
Anyway, I'm going to install it and give it a shot now. Wish me luck!