Monitor/GFX card going into standby

[blue4ice]

Setup: -
Gigabyte GA-P35C-DS3R
2gb Corsair RAM
E6750
Sapphire 1950Pro - 512mb - passice cooled - Artic Accelero S1
Latests ATI drivers installed
All back to stock

I am getting a problem when playing games (first noticed during crysis demo and now in need for speed pro street). I will be playing away and then the monitor will go into standby mode. I get the message no signal detected come up on the monitor and the power light then turns to orange.

The above two are the first proper games played on this setup since I have built it. It has been running internet/office apps fine so I wonder if it is something to do with heat?!?!? The HS is warm to touch but not hot.

Any help greatly appreciated as I want to play some games whilst off on Christmas break (and the mrs is at work lol)

 

[blue4ice]

For further information this is the power supply that I have
http://www.nexustek.nl/NXS-nx8040modular80pluspowersupply400watt.htm

After looking at the specs I am unsure whether this is man enough for the gfx card. Interestingly though after reading around on other boards this does not seem like an uncommon problem for this card