login problem

Dear friends,

I am using linux redhat nash version 4.2.1.6 os.

now i rebooted my system suddenly the following error is coming.

INIT: canot execute /etc/X11/prefdm.
INIT: canot execute /etc/X11/prefdm.
INIT: canot execute /etc/X11/prefdm.

after that it is asking

login :

there iam giving root but iam not logging in to system.

anybody please help me.