keyboard and mouse keep freezing

i have just built an amd athlon x2 pc. while trying to load windows i had to remove one of the ram sticks to get it to copy the installation file. when i finally got windows started i found that the usb wireles keyboard and mouse keep freezing. I have to unplug and replug it to get it to work again. sometimes it just freezes for a couple of seconds and sometimes it wont unfreeze. Has this got something to do with faulty ram or could it be a motherboard or psu problem?