[lesleyjacques]

I have 2 Iiyama ProLite E2407HDS screens running off a MacPro (OS 10.5.8). Both screens and mac were purchased in February this year.
Periodically, both screens turn blue, then black, then blue, then black, before the picture comes back. First the left screen, followed by the right. this whole sequence takes about 15-30 seconds, and seems to happen at random intervals.
The screens have always done this; at first it happened occasionally, but the problem seems to be occurring more frequently (or maybe I've now run out of tolerance).
Is there a simple fix before I call the manufacturer?

Any insight gratefully received!

[Cold Warrior]

does it happen if only one screen is connected?
does it happen if you change (reduce) both monitors' resolutions?

could be a bad dvi cable.

Another step would be the apple hardware test, which came on CD/DVD with your Mac Pro.