Mouse/Keyboard unresponsive right after boot

Hi!

I am having some trouble on running Snow Leopard in my AMD machine (specs below). When i boot up, everything goes ok, it shows up my desktop. But right after that i can't interact with GUI for like 5 minutes, but i can still move the mouse cursor. After that, the system works flawlessly. You see that is not exactly a boot problem, and at this time that the mouse/keyboard does not respond, the system seem to be working fine (if i stick a USB drive it recognizes it on the go, and sometimes Apple Updater shows up).

It doesn't seem to have anything to do with the SL version, since this problem shows up since 10.6

I have tried Retail install and Snow Hazard, the problem was there both times. Can anybody help me with this?

My Specs are:

CPU: AMD Phenom II X4 9600 Black Edition (AM2+)
RAM: 4GB
Motherboard: Foxconn M61PMV**
Chipset: nVidia nForce MCP61
Graphics: nVidia GeForce 9800GT - 512 MB - GDDR3

** i have seen the same problem on people who has the same MoBo that i do

Thanks!

Anyone? :(