problem with ichat

FROM : denis ravizza
DATE : Wed Apr 13 13:55:38 2005

Hello All

My Ichat is not running, can someone tell me what is the meaning of
this error message I get when I click on my contact in iChat :
NSInvalidArgumentException:
NSConcreteMutableAttributedString addAttribute:value:range:: nil value

and how can I get it to run again

Thanks
Denis