Distorted output when using Pro Tools

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I have a MacBook running OSX 10.9.3 with Pro Tools 10.6.8.

I've been using the Eleven Rack as my interface to Pro Tools via USB for the past year with no real issues, monitoring only via the Rack's headphone out. But now when I try to play, the audio is horribly distorted (not like clipping, no levels are clipping). If I plug straight into the Rack and just come out via the headphone jack to monitor (w/o using PT) I have no issues in sound quality. But the moment I try to use PT with the Rack, the output becomes extremely distorted. I can usually use it as my interface to monitor any of my PT sessions, but now, anything that leaves Pro Tools and hits the Rack is useless. Note, that if I use PT w/o the Rack I have no audio issues. As a test I recorded a riff while the output is distorted, then quit PT, turned off Rack, reopened PT session, and the riff I recorded sounds like it should, no distortion, so it's only happening at the output. ALL audio that is output is distorted, not just guitar.

So here's where I think the issue stems from. Just this week I had to upgrade from OS 10.6.8 in order to install Native Instruments Komplete. The issue started the first time I attempted to use the Rack after the upgrade to Mavericks. I've downloaded the newest driver from Avid's support page (ElevenRack_1_2_0_Drivers_80532) which is supposed to make it compatible with Mavericks, but no luck there. I've uninstalled and reinstalled drivers but don't know what else to do.

Looking at the User Options on the Rack's display window, I have the latest firmware version:
Eleven Rack Version 2.0.1, Build 0.1.5.7

Looking at Eleven Rack in my Mac's System Preferences:
Firmware Version: 2.00.1
Software Version: 1.2.0

Any help is greatly appreciated. Thanks.

[Benoni]

What USB port is the Eleven Rack plugged into? Have you tired a different USB cable?

You may want to look over this as well
http://avid.force.com/pkb/articles/e...oductCategory=