Problem with my XFX 5850?

Hi, I recently purchased all brand new components for a fresh computer build about 1 week ago.

Here are the components:

Intel Core i7 930 @ stock settings (cooled by a Zalman 9900ALED)
Asus P6X58D Premium Motherboard
Corsair HX750 Power Supply
G.Skill Ripjaws 2 X 3 GB (6GB) DDR3 1600 RAM
Antec Twelve Hundred Full Tower Case
XFX Radeon 5850 Video Card
HP 2159m 1080p 21.5" LCD Monitor (1920 X 1080 resolution)

All of this is running perfectly fine on Windows 7 Home Premium 32-bit. Browsing the internet, playing HD videos, and just opening files and programs is very quick compared to my old dual core computer.

The problem comes into play whenever I play a game. I usually play World of Warcraft almost every day and I tend to get anywhere from 40 fps to 60 fps (depending on where I'm at) when all settings are set on Ultra (minus the shadow effects). The problem is that on some occasions, the screen will sort of flicker as if there is a bad connection. I can confirm that this occurs on DVI and HDMI connections. Now, remember, this only happens when I am playing WoW. In fact, I have played other games with the absolute maxed settings on them (Half-Life 2, Borderlands, etc.) including the highest AA of around 8X or 16X. I seem to get at least 30 fps just from looking at the smoothness of gameplay. I havent noticed any flickering in any games besides WoW. Also, sometimes the flickering is bad enough that it flickers for like 1 second and the screen goes black. When this happens, I can sometimes manually open the task manager to close the game out and everything will be fine again.

The thing that worries me is that sometimes, when I start the computer up, the screen is shown in a shade of green. Everything shows on the screen fine whenever the bios, etc. are loading up to get to the OS, but it's just in green. This only happened to me twice so far but that is a lot considering this computer has only been built for about 1 week.

Also note that I play my games in the maximum resolution of 1920 x 1080 that my monitor can display.

Again, everything works very well when this problem does not occur but when it does occur, you do notice it. This isn't a problem of things like artifacting or anything like that. The graphics card generally stays anywhere from 35C to 40C when not playing games and goes between 38C to 45/50C when playing games (depending on the graphics settings and how long I have been playing, etc.)

If I have to, I can use the MemOK feature of my motherboard to test my ram if that can be causing this. I have also not tried using stress-testing programs yet. To me, this doesn't seem to be an issue of overheating since the temps stay fairly low most of the time. I am currently not overclocking anything on the computer and the CPU stays cool at around 40C most of the time (45C+ sometimes while gaming).

I have the latest version of the Catalyst drivers from ATI (not XFX) and have been using the Overdrive feature to modify fan speeds a bit. That is all I have done with the program; no OCing or anything of that sort.

Hopefully someone can help me with this. I'm hoping that this is not a case where I will have to RMA and use my warranty with XFX. If anyone needs more information about my system, just ask me. :-)

Edit: This is my very first build in terms of "from the bottom up." I have replaced things like ram and video cards before but this is the first time I have completed an entire computer build from scratch due to finances.