samba - Mar 2006 - Badusername error that reboot the machine

I have a Red Hat 7.1 system with the Samba version that came with it. The
problem that I have is:

"login(pam_unix)[11088]: bad username
[Û[oÛ[kííë[uw¿o}w¿omou\177¿{uou}{u¿·¯½¿¯[u}woow­íëku{ouo¿»¯·¯»­»¿oo¿}o¿m·¿·í
ëíë{u{_owu{o¿oowmo»¿Û[oÛ[kííë[uw¿o}w¿omou\177¿{uou}{u¿·¯½¿¯[u}woow­íëku{ouo¿
»¯·¯»­»¿oo¿}o¿m·¿·íëíë{u{_owu{o¿oowmo»¿Û[oÛ[kííë[uw¿o}w¿omou\177¿{uou}{u¿·¯½
¿¯[u}woow"... and continues.

I don´t know how this text can reach the samba login and I have other
problem in certain moments the system reboot because the frequency increase
until the system reboot automatically.

Greetings, Antonio García.