8800gtx - monitor issue

[sintan]

im havin a problem with a new build.
sometimes just as windows XP logs on and the desktop comes with all icons as usual, the monitor goes black. the pc is still running, but there's no image.
i tried the pc with a crt and the same thing happened and the monitor displayed that it was working but there was no connection so could it be the GFX card?
the problem can occur three times in a row or sometimes not for days, so its hard to test different settings. it's usually just a case of restarting, running scandisk then gettin on with things.
oddly i connected an analog lead from gfx card to monitor (as well as digital which is what i use), awaited the blackness, then turned to analog mode on the monitor and i could see an empty desktop (i've since discovered this is acting as a second monitor on a dual setup and icons would be on other monitor if using two)

setup:
Gigabyte GA-P35-DS3R
duo E4500
Arctic Cooling Freezer 7 Pro
8800 gtx 768mb
GeIL PC2-6400 C4 Black Dragon
samsung 2232bw

any ideas folks? thanks in advance

 

[sPlAtOiD]

Try to run just your VGA side of your card to see if you still have the same problem. Also try to start in safe mode with your DVI cable to check if it still loses signal.

 

[sintan]

i'm using corsair 550w...

ok i tried vga last time it went black but the switch from digital did nothing this time. i'll try it with vga alone, but like i said it's hard to diagnose coz it's so sporadic. thanx for advice

 

[optimist4613]

Good PSU = Good graphics end off

 

[sintan]

ok but from what i can gather i'm using a fine psu - Corsair 550W VX.
when the pc boots up without a hitch (which is much more often than not), i can play crysis and such without problems