I'm having a weird problem with a RHEL6 workstation. When the screen lock is activated manually the system will lock and the screens will go blank. Once I try to unlock the system, the monitor will just flicker and won't respond. I tried the combination CTRL, ALT, Backspace and it did not work, I also tried CTRL, ALT, F2 and was able to get a command line but was not able to return to a GUI session without rebooting the system. Does anyone know how to fix this issue or can offer any advice?
What type of monitor? Did you try a different type of monitor? Is there an led on the monitor? For example, when the monitor is own is it green? Does the led ever turn off or is amber?
The system has 2 Dell 22 inch monitors, the left monitor is primary and does not turn back on, the right monitor turns on but just flickers. Once the system is rebooted then both monitors work perfectly.
I found the fix to the problem. Basically in the /etc/pam.d directory the system-auth file had the wrong permissions (400), after changing the permissions to 644, the screen lock worked as it should.