Game freezes at resolution change

Hi,
I'm having this issue since I bought my new pc: at every resolution change of the game there is a good probability that the game freezes and I have to close it via Task Manager.
By resolution change I mean when I join the match and it starts loading the map or when the match is finished and it loads the result page screen.
I tried both windowed menu or full screen mode, the problem is still there.

The configuration of my PC is:

Motherboard: Asus M4A89GTD PRO/USB3
Processor: AMD Phenomenon II X4 965 3.40GHz
Graphics card: Asus Nvidia GeForce GTX 570
RAM: 8GB
OS: Windows 7 Home Premium 64bit

The desktop resolution is 1680 x 1050 with Refresh rate:60Hertz, Colors:true colors (32bit)

The game resolution I tried are 1280x800 and 1440x900 with Color:32bit and Texture:high

Hope you guys can give me some hints cause I'm getting frustrated!!!

Tnx in advance,
Enrico.