Where is Timo Lässer?

I seem to have a font problem. I see that some links to user profiles go via their user number, some by thier user ID. So if I click on

then no problem, but if I click on a lik such as
http://dynamicsusers.org/members/Timo+Lässer.aspx then the link gets converted to http://dynamicsusers.org/members/Timo+L%c3%a4sser.aspx which is not accessible.

So basically the ä is causing a problem. Is it just my browser, or is it a site issue? If a site issue, then maybe we need to block special charachters from log in names.

Timo, I hope you don't mind me using you here, but it was the first name with an Umlaut that I could find.