ok. next question... do you have stereo interleave on or off in the master bus and if so, is there any diff?

I had stereo on.  If I switch to mono (with the master panned hard left) same result - faint signal out the right monitor.

would you be willing to post the project file somewhere so i can take a listen?  promise i will not infringe on copyrighted material!  
pm me a link if so.

I would if I thought that would make any difference, but like I said I can reproduce this issue with a brand new project, no plugins, no nothing.  Just pop open a new project, get some type of sound in there from any source, and this occurs.  Reproducible across multiple projects, new and old.

right, but i don't use a babyface so that takes one factor out of the equation.  two, i don't use the same studio monitors as you so that takes two factors out of the equation.  three, my production room is shielded in 4 inch thick plates of lead in the event of nuclear attack, so cellphone towers have no effect. (just kidding!)  really, at this point there's only so much that someone can answer without a project file and a different audio interface.  

Ok, well now I'm jealous of your bomb shelter/studio!  Here's a really pared-down project, just a click panned hard left going into the master which is stereo/centered - keep in mind I really have to crank my interface to 11 to experience the effect I'm describing.  Not sure if this will help but I appreciate your willingness to troubleshoot.
 
http://kybernetos.com/TestProj.zip

Cool. I'll take a look tomorrow. Actually therr is a way to check. I'd export the file (and i will) as a wav then open in audacity to check the wavforms. If there is data in the right channel then likely sonar. If not... Who knows...

Just a quick test...
 
Delete the bus (master) and insert another one.  If it not too loaded.

I just loaded the project. I set the master bus meter range to 90 dB and didn't see anything. So then I panned the master bus output full right to hear only the right channel, put on headphones, and turned the interface headphone level up full blast. I couldn't hear anything.
 
Then I bounced the click track to a stereo track based on the master bus settings, set the left channel gain to minus infinity, and normalized the track to 100%. If the right track had anything, it would have been normalized up to something audible...still nothing.
 
There's definitely no interchannel leakage within SONAR. However, the click level is really hot. Are you SURE it's not audio crosstalk within the interface or some other element of your system outside of SONAR? 
 
As I mentioned previously, crosstalk specs of -55 to -60 dB are not uncommon. You can hear tape hiss easily at -60 dB and -55 dB is about the S/N of AM radio stations. With a hot click level, you could definitely hear it in the other channel if the levels were turned up...probably even if the crosstalk was -65 or maybe even -70 dB.

I'm not getting any bleed either, through my onboard audio with 3 sets of cans or my FTU with monitors or the same cans.  I'm guessing it's the babyface.  Are you using the phones out or the outs on the breakout cable?