jpetersen
Craig, in your Week 35 tip you have a red box around the Realtek driver (which is shown as disabled) but also the AMD HD audio device, which is NOT disabled in your screenshot.

 
The driver is being disabled in the screenshot, i.e., it's not disabled but the menu to disable is has been chosen and the cursor is pointing at "disable."
 
Also note that the two-step nature of this process that involves both System Devices and Sound, Video, and Game Controllers. It is not always necessary to do the enabling/disabling in System Devices but the described procedure insures that the unwanted driver won't turn back on.
 

If I look in the same place on my DAW, I also have a Realtek (which I now have disabled, same as yours), and similarly a "Intel(R) Display-Audio".
Are these also supposed to be disabled? (I ask, because your equivalent driver is NOT shown disabled.)

I would suggest disabling it temporarily and see if it makes an improvement. If it's some kind of system thing that causes a problem, re-booting should restore.
 
If it does make an improvement, re-visit the procedure and make sure you've followed all the steps. When you reach the point where you have the option to disable "Intel Display Audio," disable it.

guyshomenet
ASIO: Using the ASIO driver that Lexington provides for the Omega interface.

You do mean Lexicon (version 2.7) not Lexington, right? Lexington does not provide any drivers.

@Craig Anderton: Thank you.

Yes, sorry ... Lexicon (brain fart on my part). ASIO drive 2.7.0.

I would try the WDM driver mode. I tried 2 Lexicon interfaces and never could get the ASIO drivers to work. Both of them went back to the store. I think the drivers were poorly written. Hope you have better luck.

Additional diagnostics:
 
I cut to MP3 exports, one with the amp simulator and one with the distortion pedal (see notes above). The same degree of cross-channel distortion was present in the MP3 files.
 
Perhaps there is something I don't understand about Sonar, but I would think that rendering the MP3 files would not have real-time, latency dependent issues. Since the induced cross channel distortion occurs in real-time (output over the Lexicon) and in the MP3 file, I think something else is afoot.

Set the guitar track input to "none"after recording.See if it goes away and report back.

You don't describe the type of distortion, but I wonder whether this is connected with your OS's Power Options. I find that Sonar glitches very easily if any degree of Processor Power Management is engaged. Go to Control Panel - Power Options and ensure that you are using a High Performance option. If you want to go under the hood look for Minimum Processor State and make sure it's set to 100%.

ChristopherM
You don't describe the type of distortion, but I wonder whether this is connected with your OS's Power Options. I find that Sonar glitches very easily if any degree of Processor Power Management is engaged. Go to Control Panel - Power Options and ensure that you are using a High Performance option. If you want to go under the hood look for Minimum Processor State and make sure it's set to 100%.

This is likely more of an interface issue than a SONAR issue, so it's worth doing if you also use audio programs other than SONAR.

I'm not convinced that Sonar is not implicated (at least in my case) although to be fair I rarely run Sonar without audio. Other software (albeit less demanding) does not seem to create the situation. That said, it is no big deal. I have Power Options pinned to my start menu, so it is a matter of seconds to switch to flat-out if Sonar (is involved in) glitches. The glitching immediately stops - I don't even have to stop the transport. I made the suggestion to OP largely because it is so easy to try, and if it solves OP's problem that would be great.