This is practically pointless but I have the same issue when trying to play music through it.
All drivers are up to date and the signal chain is: PC --> UX2 via USB --> speakers via headphone jack.
Sounds the same when I plugin my headphones instead of the speakers.
The sound gets better when I mute the right or left channel inside the windows audio mixer. As soon as I pan in both channels it sounds stupidly weird again.
I've also tried it with my POD HD500 and the issue is exactly the same.
I just think that Line 6 didn't provide the correct drivers for windows or doesn't know/want to fix them.