New LCD Filckering

Hello,

I have a brand new (about a week old) Samsung Syncmaster 743Nx LCD screen.
I've noticed ever since I hooked it up that when I first turn the computer on the screen will flicker. This will last for about 15-20 mins and then it goes away, although i've also seen it come back then go away again after a while.

Is this an issue with the LCD screen? or is it with other things like the video card or power supply or even the VGA cable?

I have a 350W generic (no name) power supply that's fairly old and a Nvidia GeForce 7200GS graphics card.