5670 problems. BSODs, artifacting, driver resets...

So i updated an older computer with a Sapphire 5670 512MB GDDR5.
It was giving me all sorts of problems so i checked the psu and realized it wasn't strong enough (or so i though) and upgraded it to a 430W antec earthwatts.

But... same problems.

Here's what's happening:

-CCC is very hard to install. It likes to crash during installation and took several tries to work properly. I've tried re-installing it many times, using driversweeper and ccleaner in between. I've also tried installing the drivers through the device manager but it always give me an error.

-It often blue screens or freezes then gives a "driver has restarted" message. I've yet to identify exactly what sets it off, but it happens on the desktop, in games (especially when in menus) and on pretty much every other application.

-I get artifacting (either in the form of lines across the screen of squares) especially at system startup. It usually fixes itself after a driver crash/reset.

The computer is an Acer pre-built, AM5620-E5523A, with the parts mentioned above replaced. The previous 3650 had no problems.

It's running windows 7 64 bit.

A possible related issue is that furmark won't run, it says "load library failed error 998. Invalid access to memory location".

Anyone have any ideas? Ask if you need any more info.


EDIT:
Ok, i've tried something that kinda fixed it. Somewhere on toms someone had a problem where the gpu would under clock itself too much at idle and cause system instability so they changed it by editing some files.
They were using an older version of ccc so i had to change some of the steps. I ended up changing two lines in C:\Users\myname\AppData\Local\ATI\ACE\Profiles.xml to make it so my card idles at 200 core clock and 400 mem clock. This fixes the problem only after ccc has loaded. My computer turns on to an artifacted login page, i log in and either it bsods or driver resets when ccc loads. If it driver resets, my computer runs fine.

If possible i'd still like to fix this. Should i be RMAing?