I am having to exact same issue... anyone have any thoughts, or solutions?

My working solution ...until now...

- install the latest driver (7.1.9) problem is still present after that on 10.8.2 but in my case it's coming an going in period (maybe a minute...)

- go to system preferences -> Line 6 Audio Midi-Devices then try to INCREASE THE BUFFER SIZE

...after that I played on instrument input about 10 minutes without any crackling/ artefacts... Good Luck! Please let me and people know If it works!!!

...Never touch a running System... it's hard to learn that... I just upgraded from OSX 10.6.8 to 10.8.2 yesterday... I thought after that long time since the release of 10.8 all heavy problems should be solved... Now I am thinking about going back to my Time Capsule Backup of the latest Snow Leopard state... Since Mountain Lion there are many performance lags... slow Logic Pro 9 GUI and now this UX2 crackling Problem... I hope it's gone now...

Short Info about my System:

Macbook Pro 13" (early 2011) • OSX 10.8.2 (Mountain Lion) • Logic Pro 9 (9.1.8 1700.67 32-Bit Mode) • Line 6 UX2 (Driver 7.1.9) • second Full-HD Monitor via DP/HDMI • also using Apple TV...

Hi there, I am having this problem to but It only occurs around 50% of the time. When I boot up Garageband I then plug my UX2 in and it seems to work, however whenever I try to use another application, like playing a youtube video it crashes. Thinking of getting a presonus next time as I don't really use Pod Farm. Hope they fix it while I save though!

I had the same issues and couldn't sit around waiting for Line 6 to help so tried a few things and I have some solutions

SOLUTION 1: Apogee One purchased and installed - works fine!

SOLUTION 2: I used time machine and rolled back to Snow Leopard.  UX2 now working as normal.  Not ideal though because data added to apps such as Aperture during the Mountain Lion period was not accessible, so.....

SOLUTION 3: Created a 60Gb partition on my Macintosh HD. Made a clean install of Mountain Lion on the partition.  Downloaded most recent drivers (Sept 2012) and the UX2 is now working as normal for the last week and no signs of distortion. No other 3rd party apps such as Spotify, Skype, Flip4Mac, RealPlayer, LogMeIn were installed in the partition - just ML and Line6. The bare minimum for making music. Likelihood is that the problems are caused by either upgrading from previous OS to ML, upgrading from previous Line 6 drivers, conflicts with other apps.

I hope this helps some of you

Nigel

iMac

10.6.8 (Snow Leopard) & 10.8.2 (Mountain Lion)

3.06 Ghz

4GB

Hello,

We have just released our latest Mac driver v7.2.1 for Mac OS X to fix the problem where USB Devices become unresponsive after using POD Farm, recording/playback in a DAW, or using other audio programs.

This driver also includes changes which may improve the noise or distortion issues some OS X 10.8 customers have experienced.

Please use Line 6 Monkeyn to update or download the driver directly from our website:

http://line6.com/software/index.html

If you continue to have problems with audio using our latest 7.2.1 driver for Mac OS X, please submit a support ticket:

http://line6.com/support/tickets/add.html

Regards,

Line6Hugo

Hey everyone. I think I might have an answer. First of all I must state, I do not use any Line6 software nor am I in the music game. I fool around from time to time but that's about it. I'm a professional cisual artist first and foremost. Like I said, I might have something for yall to all try. Let me explain my audio issues. For the longest time I stayed on Snow Leopard 10.6.8. Probably the best OS know to man, haha. Anyway, I "upgraded" to Lion 10.7.2 and had TONS of audio issues, I reverted back to SL. Aside from my professional gig I play MMO video games quie regularly and one of the games I play is no longer going to be supporting anything below 10.7 Lion. So I upgraded to Mountain Lion... and guess what? Audio issues EVERYWHERE. I was fearful that the audio might become an issue with working in FCP and it certainly became an issue when doing any kind of recording. The most noticeable was in Garageband, crakling and popping was everywhere whenever I used 3rd party VST or other plugins. I searched and dug on the interwebs and only found other people with the same issue. I put 10.6.8 on a partition and just switch OSs if I needed to do something with audio. That's when it hit me. I remember reading somewhere that some people supposed the issue was related to USB 3.0 support on older machines without USB 3.0 ports. Something to do with the core audio component. I made a copy of the core audio component on the Mountain Lion partition then took the Snow Leopard core audio component and overwrote it. So far everything is working wonderfully now.

TL;DR version

1. Make a copy of the core audio component in Mountain Lion (keep it somewhere safe)

2. Overwrite the Mountain Lion core audio component with the one from Snow Leopard 10.6.8

3. Hope it works!

(the core audio component is in /system/library/components/CoreAudio.component)

GOOD LUCK!