Mike... I use these headphones as well and they work fantastic for isolation for vocalists or even better for drummers when the kit is huge and loud to begin with. We call them the 'headcrushers' lol!!

Rev Bob, I'm no pro at Sonar or anything, but I'd like to share some of my personal experiences with you regarding your issues.
 
1) New project - started with a single, mono, audio track, did a second take but the first take kept playing, even with the mute on the take lane. I had to save and close, then reopen. Worked fine next time.
 
Uggh, yes I get this all the time and it drives me absolutely crazy. Now, I can only speak for myself on this but it's the only time I've seen this happen and I don't even have to use take lanes. So I'm working with a vocal track. I have the singer do various punch-ins. If we need to tune a section, I split the clips and run V-Vocal on it. When I "bounce" V-Vocal to the clip it processed (I do this one at a time) it sometimes puts a muted clip over top of the V-Vocal correction clip. It should put the muted clip (which is the original vocal clip) behind the corrected clip. Sometimes it does, sometimes it does NOT.
 
That said, there are times when I use the "K" key to mute sections of the vocal track. When I do this, some sections of it play back even though it is muted. I go into take lanes and sure enough, something is playing. Take lanes in my opinion, are messed up. I don't even have to enable them and they seem to take on a mind of their own. So yes, I sincerely believe this to be a bug. I personally have not filled out a report for it. The reason being, at this point I'm not even sure we'll see an X2 b so I figured why bother. Getting information out of Sonar is like pulling teeth. Granted, these days it's hard with all that has been going on in Boston...but for crying out loud, is it so hard to post a message up here that there will or will not be an X2 b for people? I just don't get all this hush hush stuff within this company all the time. Sorry to vent about it, but after all the years I've been using Sonar, I'm honestly tired of always living in the dark.

2) This has happened a few times. I had a few tracks where at quiet moments during a vocal you can hear a bit of the click bleed in from the headphones. I liked the takes so decided to use Izotope RX2 and apply FX to clean up these sections. I found that I could not use this if there were Take Lanes on a track. I had to delete lanes or move vocal take to another track.
 
I can't say for sure, but I would THINK this is normal behavior. There's no way for Rx2 to know take lanes are being used. It needs one solid line of audio and that's how I use it on my end. I have RX2 in my Sonar utility options. I hi-lite a track, press utilities, click on the program of my choice and it exports the wave right into whatever program I want to use.
It looks like this:
 
If you're interested in this ability, you can grab the utility to make these items show up in your configuration menu here:
 
http://www.digifreq.com/digifreq/downloads/SetupSonarUtils__302.exe (Thanks to Scott Garrigus for turning me onto this and for hosting it for all these years)

 
3) Random crashes when opening Izotope Ozone, or Stylus RMX. Only once in a while, doesn't seem to reflect any strain on resources, no consistent pattern.
 
I can't comment on this one. When I have used Ozone, it never gave me any issues. I don't use Stylus.

 
4) Had 2 projects where I could not open the VST instrument(Kontakt and Stylus on another)) to edit parameters. Had to close without saving to access these instruments after reopening and adding the VST's again.
 
I've not had that problem with Kontakt, but it's given me more grief in Sonar than any other VSTi hands down. I hate Kontakt so bad, I'm going to throw a party when something comes out that blows it away for the stuff I use. It works about 90% of the time for me. That 10% that it gives me trouble is 10% too much. Sometimes I load a project that has Kontakt in it and Sonar will crash before it even opens. Close it, reopen, it's fine. If I run too many instances of Kontakt using Sonar 32 bit, it crashes itself and Sonar where all other synths I may run into this problem with will give me an out of memory message without crashing anything. I do use Sonar 64 also but only need it on the rare occasion.

So yes, I do believe some of your issues may be bug related...some may be related to our hardware or configuration. It's tough to tell really...but one thing is for sure, the take lanes thing as well as Kontakt would definitely be solid suspects to me. Then again, not a lot of people complain about Kontakt. But quite a few have complained about take lanes.
 
-Danny

Hey Danny - thanks for this. A little affirmation I'm not going crazy is good every once in a while. I'll definitely look into the Utilities option - seems like something that would work well with my work flow ( I use Melodyne and Audition as well).

I have noticed that even if I delete all the take lanes, sometimes the Take Lanes button remains highlited as though they're still there. They seem really inconsistent. I like them better than stacks of clips (sometimes I can't find a clip when its layered), and have been happy with the results when layering midi takes, but the inconsistent behaviors when recording audio are a pain so far.

I have had a few issues with loading VST instruments before in X1, where I would get the wrong VST loaded, but current issues are new to me in X2. I really can't live without Kontakt, so NI has me by the b@lls.

Thanks again.