I made this post because this is something I have been having troubles with over 3-4 years. I have had many problems with the toneport UX2 version (I work with a windows 7 64 bit system). But two problems have never gone away: a crackling popping sound after X number of seconds and after a couple of hours it would crash and freeze my volume, making me restart the computer.
In my case I noticed that the crackling sound may appeared when I was doing something on windows. After searching a lot of forums I found a program that could analyze the DPC latency of a system: go here http://www.thesycon....ncy_check.shtml
It will give you information if your system can handle real-time audio/video service. By disabling devices in device manager one after another, I had found my problem for the crackling sound. After disabling my ethernet driver it dropped right into green and I have never heard a crackling sound again.
After a day the volume bar hasn't crashed either. After research I think this comes because windows cannot handle a continues data stream over USB. This comes from a security update with a bug. You can try to restart the audio service through CMD with the following commands: