sir, i m using rhel-4 and facing one problem.. the system boots into the runlevel 3 mode ,,, but wen i issues the command telinit5, the screen gets blank. in the inittab the default runlevel was 3 first.now wen i have changed that to 5.. the system boots up.. as sson the login scrren comes up.. it again disappers. i cheked xfs is running..

now was happening is even i log into the single user mode.. the prompt is not shown the screeen goes blank... but if i use intractive startup, press shift key than the shell prompt comes. and if i restart the xfs .screen asgain goes blank... kinldy help me...

try checking if you have the Xorg.conf file. use the system-config-display command to create a new conf file, not sure if that works in runlevel 3 though. But I think your missing the xorg.conf file.
and just check if xfs is running in level 5
otherwise..
chkconfig xfs on