Replacing a cable may actually some times help. I have been having mysterious blackout issues with by Benq FP-241WZ for a long time (not in the beginning).
I've read about it but never believed. As I today once again read about the same solution, I decided to give it a go. And yes, changing the DVI-cable resolve the blackout issue!
I guess Benq did a good monitor but bundled it with a poor DVI-cable. The one I used was supplied by HP.