I'm very new to all this, so possibly a silly question but what exactly does Geeklog do?

Go to the main page of this site http://www.geeklog.net/ and look for the box that says "About Geeklog" and read it.

It says nothing about "Do NOT use spaces" in a username, although in the admin section, it clearly states it....and I have had problems with people logging in after using spaces despite not knowing they shouldn't....