Username validation problem

[die]

Hi,
I have migrated the users of my old forum to joomla (kunena instaled), everything works fine except for the usernames with blanks.

Joomla does not allow to register a new user with rare characters or spaces in the username, but I have many users imported that way.
They can logg-in but the problem is I cannot make any changes on that users from the back-end because joomla re-validates username and I get "invalid username" when I try to save changes.

Where in joomla can I change that validation rules?

Thank you

[die]

Hi again,
some of my users ran out of assigned group (even "registered" group) and I don't know why.
Just a few users, any idea?

the big problem is that in some i assigned the group/s again and that is all, but in other I can not save changes because of the username (in example those who have blank spaces in the username)
I have posted other topic with this issue.

thanks

[pe7er]

[mod note: similar topic have been merged. Please do not create new topics for similar problems]