I don't think that sounds like the same error at all, my screen switches
off and depending on what is going on doesn't switch back on right away
(like that one time when some process didn't start up and I had to ssh
in to poke it)

Nevertheless, I tried applying the patch, and the result was identical..

Then surely it comes down to an issue with either *your* video controller card or monitor. Please now try the obvious, follow scientific procedures and swap them out, one at a time. Clearly, it is a hardware problem and nothing to do with CentOS - unless you can convince me otherwise.

Alan.