I don't know what the different refresh rates are but mine runs at 60Hz (I think it does higher ones too but this was the default) and the picture stability is superb, not a hint of flicker at all, when there is just my wallpaper image showing, it could be a painting
If the monitor is switching off it could be losing the output from the graphics card which will put it into "power save mode" (same as if you unplugged the VGA input lead from the PC) which also points to a dud graphics card as somebody else suggested.
You do need to choose the right res though - I had mine at 1024x768 when I first fired up the computer and it was horrible, but at the designed 1280x1024 its lovely.
I hate widescreens, but that's just me. I always think you can fit more useful stuff on a proper shaped screen which was one reason I got this HP.