authentication protocals for Mac

[Shadi Pakatchi]

Hi,
I'm a casual network administrator and need help. My
power g4 is asking me for login on a black screen with
cursor and the operating system isn't visually
loading. 

Is there someone who could help me resolve this
problem? Apple is of no help.

I think it might be kerberos... 

my ip is connecting to another server called Darwin
BSD as a (console)

thanks
Shadi Pakatchi