Username unavalible... But it is!

First topic message reminder :

I only have 2 members on my site, since we started early December. I invited my first member to join, but the first username they tried was "already in use" when I knew that it was not. Then, when I tried to create a test account, the first username i put in for registration did not work because it was "already in use" when I know that it is not. I am worried this may be driving away potential members of my site, and I want to know if anyone knows how I can fix this.

*Solved - thanks to all who helped out, turns out my forum is a little... challenging. But thanks to everyone!*

For security issues, those usernames are considered.

Topic Solved & Locked