Why does my wireless keyboard keeps disconnecting?

I have a wireless track pad and keyboard (no number pad) that I use at school. I have to use a usb bluetooth adapter because the Mac Pro the school has does not have native bluetooth. My trackpad works flawlessly but my keyboard has problems. Most of the time it can not connect at all and the few times that it has connected it disconnects very soon, even while i am in the middle of typing something. This is very annoying. I have changed the batteries with a fresh pair and still the problem persists. Please help me, this is very aggrivating.