Computer Issues Maybe Memory Or motherboard or CPU Or PSU

anyway, I need help..no ideal where to put this topic but i need alot of help, I have a 3 month old computer, built it my self and very happy about it. BIOSTAR MCP6P3 AM3 NVIDIA GeForce 6150 / nForce 430 Micro ATX AMD Motherboard, with two 4GB sticks 1066 1.5v of RAM, AM3 Processor and good stuff. few weeks down teh road, the computer acting weird, did some reserch and found out the memory was corrupted..sent it back got new ones..worked fine. two weeks later..computer was so bad that it wouldn't start with 8 gigs of ram in the computer, took one out..no big deal..was ok with it, thinking bad memory..then..all heck broke lose. USB started failing, as in mouse would not work, at all some times, something would happen that the mouse and keybored would just..power down.. I need to know, whats going on, did i get a bad MoB? I am not overclocking anything, so i am lost why has everything gone down the drain.