Xorg display locks after idle time

[Alex Regan]

Hi,
I have a fedora21 box and periodically the display stops responding. The 
display on the monitor is blank, and trying to wake it again with the 
mouse or keyboard is not successful.

I can VNC into the system, and while the screensaver is on with the 
clock in the center, the clock does continue to update.

It's like my keystrokes aren't being acknowledged, I'd say.

I can access the system remotely via ssh. I've tried killing Xorg, but 
nothing changes. It just comes back in this screensaver mode and the 
monitor is still unresponsive.

I'm using the default driver that's chosen at install time for an ATI 
Radeon chipset.

I've looked through the Xorg.9.log file and there is nothing indicating 
any type of helpful error message.

How can I troubleshoot this further? Perhaps it's a known problem?

Thanks,
Alex