EDIT: Problem solved, thanks. It was the Eco sensor that thought I'd gone away because I wasn't standing close enough to the monitor, so it turned it off.
I think that a new 24 inch Benq BL2400PT I've bought is faulty, but I'd appreciate yr views. It's not something I've seen before.
I've tried it on my new system with Win7 Pro 64 bit and my old one with Win XP 32 bit, and the same thing happens on both.
The system boots and displays the BIOS info, then goes into Windows, adjusts to 1920 x 1080, looks fine for half a minute or so, then , a small sundial/timer thing appears in the centre of the screen, it goes round like the fingers of a clock, then the screen goes dead and the no signal green light starts flashing on it.
But if I hot switch my other monitor, the Asus AL1916, 19 inch, into the computer, the windows screen displays as normal, plug the Benq back in, screen displays with timer thing, then goes black .
Same on both computers, different specs, different OS.
Can't be a driver problem as it works initially.
It's the timer thing that's bafflling me, but I guess that must come from within the Benq monitor. But I'd appreciate confirmation that it's not something daft I've missed before I ring Ebuyer and go to the trouble of sending it back.
This is a picture of the timer thing if it helps
http://www.upload3r.com/serve/131110/1289661426.jpg