Username wont read?

Alright so i have a user who didn't have a problem with it before, but has now: he can't log in with his username: Khá
But if changed to Khaa, he can... Why is this happening?
He was inactive for a short periode, and decided to activate it again today but couldn't because it keept teeling him that the information was incorrect. Even tried to give another password if that was the case, but that didn't work either.

Wait a minute! You said that when you changed the username the member could log in, correct?

Yea, after i changed it from Khá to Khaa he could.. but i was wondering why there was a need for it to be changed...
There havent been a problem with it before.

Have you changed anything during the time this member was inactive?

Nothing concerning letters and username.. only the layout.

Check Here:  AP > General > Censoring > Username Censoring

Nothing there, its empty :s

I wonder if the member might have typed in the wrong username.  Did the member manually type the username?

I tried to log in with his username and new password, but i couldn't either, and i copied the username from the database. It was very strange.

Could it be cause it's formatted differently? Khá

I mean the fancy looking "á".

Hello i think i know what this may be i see this with one other member before.
ACP >> General >>   Forum >> Security "Find"
Unauthorize subscriptions made with the most commonly used spam usernames. : change that to NO then save.

Now go to the following.
ACP >> General >>   Forum >> Configuration >>
Resynchronize your forum : tick the box   then Save

APE wrote:Hello i think i know what this may be i see this with one other member before.
ACP >> General >>   Forum >> Security "Find"
Unauthorize subscriptions made with the most commonly used spam usernames. : change that to NO then save.

Now go to the following.
ACP >> General >>   Forum >> Configuration >>
Resynchronize your forum : tick the box   then Save

It was already checked as no :s

ok put is as yes then try again.