I've got the same problem after setting the resolution and bit depth too high, so the monitor says "input signal out of range". However, on RedHat Linux, there doesn't appear to be a "sax2" command. What would be the equivalent way to reconfigure the resoultion?
I've looked at /etc/X11/XF.... file and seen the Section Screen and Subsection Display entries, but it doesn't seem like editing that file will get one very far, in fact, you can get stuck.
Press ctrl Alt F1
Login as root
Enter command init 3
Enter command sax2 - l
Reconfigure resolution from there.