I have the same problem, sound freezes when using either toneport UX2 or Guitarport. Farm or Farm 2.5 does not have to be running. I have
Windows 8 64 bit
USB 2.0
Nothing has worked. I was dual booting into Windows 7 and everything works as it should. I recently downloaded the newest drivers and tried again. Still doesn't work. It's not my system it's something either Microsoft did with audio in Windows 8 or it's a Line 6 issue. One thing I noticed that Windows 8 does with audio that other versions of Windows didn't do was when you unplug your speakers the speaker icon x's out and disables audio.