rank problem

Hey guys... long time no see, huh? well, I actually have a problem that's why I'm here... I've trying to give one of my members a rank but there seems to be a mistake with some kind of codes or something... I'm sorry if there is a similar topic but I don't have much time to look... can anybody please help me?
my forum's link is http://twilightmaniacs.forumtwilight.com/

PS my panel is in greek...

Admin Panel >> User & Groups >> Search User >> Pick the user you want to give a rank >> Go to to the bottom of the profile >> Look for Rank >> Pick Rank >> Save

That's exactly what I do, but it says something about a mistake that has to do with the code...?

thank you, anyway...

Can you post the error?

http://twilightmaniacs.forumtwilight.com/admin/index.forum?part=users_groups&sub=users&mode=edit&u=10&extended_admin=1&sid=831dc47fe8993ad9b01f89b71bf9bebb

I hope this is what you mean... it's in greek, the red letters mean "Wrong! The codes you gave do not fit in"

or something like that, my english isn't this good...

We need a screenshot not a link to the admin panel since we don't have access.

oh yeah thanks

oh... it's suddenly fixed... I'm so sorry for causing you this trouble... I don't understand what happened, really... thank you all very much for trying to help me... sorry again, guys...