i would try to isolate the problem before going and reinstalling OS's, etc.
you must determine if it's the ua-5 or the computer.
if you have access to any other gear like a v3 or something, test that out and see how the recording goes. if you still get the pops and whatnot on the computer you'll know its the computer. if everything works fine, you'll know there was a problem with the ua5
ian