Usernames already taken, despite knowing they're not!

Earlier today, I had a friend join my forum, so that she could assist me with the graphics.

Upon registering with her desired username of "Bastet" she was informed that the username had already been taken.

I knew that this was impossible due to the fact that at the time, I was the only member that was registered to the site.

Now, that exact occurence has been resolved the long way around, by which she signed up under another name, and I then changed her username to "Bastet" in the administration panel.

The reason for my posting here, is to discover two things.

1. Why did this happen in the first place, since I KNOW for a fact that the name was free before hand?

2. Is there any way to prevent this occuring again in the future?

Thank's for any help that can be provided.

Sincerely,
Andae92.

Hello,

There's an option in the admin panel that does this(for security reasons), you can turn it off here:
Admin Panel > General > Security:
Unauthorize subscriptions made with the most commonly used spam usernames. : Set it to No
> save

Also, you can check whether the name was already taken, here:
Admin Panel > Users & Groups > Inactive users

Thank you for the possible actions Jophy.

I had already checked the inactive names, but I wasn't aware of that security setting.

Needless to say, I've administrated a few forumotion forum's in the past, but this was the first time this problem has occured to my knowledge.

But, that's that one solved, thank you very much.