Screen blanking

[#1]

To be honest I'm not sure whether this is a hardware or software issue but had to put it somewhere.
I've been having an intermittent issue on my main PC where the screen would go blank for anything from a fraction of a second to a few seconds. This happens for around 5 minutes, then doesn't happen again for anything up to a couple of months where I end up forgetting about - till it recurs.
It seems that when the desktop reappears and I move or click the mouse it blanks again - but that may be a red herring as it also happens without mouse intervention. Just that it happens more often when I do.
I doubt if it's the HDMI cable as I have used another and I doubt if it's the monitor as I have connected to the laptop by two different HDMI cables with no problems.
Maybe it's the graphics card but I don't have any other symptoms. Apart from the above all else seems to be OK with it. No pixelation or problems with video, etc. Each time it happens I search for more recent drivers and install them just in case.
Maybe it's software and something to do with the screensaver. I'm running W7 32bit. I used to have the screensaver set to 1 minute but have now changed it to 10. I know with LCD I don't really need it but even turning it off doesn't prove anything as it could be two or more months before it happens again.
Has anyone experienced anything similar and found a cause and a solution.
Thanks

[#2]

Sounds like the Electrolytic caps are on their way out. I've had 2 monitors with symptoms like this (both from freegle) which I repaired.. ish. Both had 6 470uF in them and the pack I got from maplin always had 5.. at £8 per pack I wasn't paying £16 for the extra cap. Needless to say with 5 fresh it would work .. and then start to fail again after a few weeks.
If you take it to a TV repair shop they should be able to test the caps in it with a capacitance meter but repair could cost more than the monitor.
How old is it?

[#3]

Thanks for your reply, okrzynska, but I had ruled out the monitor being at fault due to the fact that even while it was flickering between screen and black I connected the laptop and problem disappeared - could have been coincidental, I suppose.
Edit: It's Iiyama ProLite E2607WS bought September 2008.