ok - first try going into single user mode
Hit enter - When you get to grub screen (Where it countsdown to select RHEL 5 automatically)
Select Red Hat Enterprise Linux with the version of the kernel that you wish to boot and type a to append the line.
Go to the end of the line and type single as a separate word (press the Spacebar and then type single). Press Enter to exit edit mode
type in the root password
next type :
If there is a line that has an ip in it delete it by using 'j' key or down arrow to that line and typing 'dd' --
If there is no line with an ip than there is another issue.
--If there is then after deleting line save file by typing ':wq!'
Finally to get out of single user mode type 'init 5'