Having problems with a new Radeon 6570 ddr3 1GB.

Hello.
I recently purchased a Radeon HD 6570 ddr3 1gb, because it's a powerful card with low power consumption. (consumes less power than a 9400gt which is my previous card, and is substantially more powerful)

Well, here's what I am encountering now. When I set the native resolution of 1440x900, regardless of what the refresh rate is, wavy lines/distortions would appear on the screen. sometimes there's only some, that it's only noticeable when you are in the desktop, but sometimes it's too noticeable that even in games you could see it.
I was on Windows 7 64bit before, and I encountered this also. Now on 32bit Vista I tried to lower the resolution to 1366 something and 1280x something and the lines were reduced/totally gone, but my computer's at an uglier resolution. That doesn't matter though, I'm just puzzled, can't a HD6570 run at 1440x900 or it's not compatible with my monitor?
Is the card defective, and soon lower resolutions would also display runny lines/distortions?

Thanks a lot.

Go to search and type device manager. In device manager click on display adapters click on it. Go to drivers, try to roll back. If tha roll back does not work, go to the mfg website and update to the most current driver

in this blog, they recommend not using a setting higher than 1280x----

AMD Radeon HD 6570 (1GB) Review & Rating | PCMag.com

However, here it shows that it's much more capable than that, if they're talking about the same card-
http://www.amd.com/us/products/desk...6570/Pages/amd-radeon-hd-6570-overview.aspx#2