I rarely have an actual sonar crash, and I rarely use midi CC 64 (sustain pedal).    Generally even in a heavily loaded project the Performance module shows low values for CPU activitiy.  
 
But recently in a very small project I've been having some lock-ups in a project that uses CC 64.    Is it possible that 'drawing' the off value (in PRV controller pain) to a low number, but not 0, can cause crashes or 100% cpu lockup?    

I just tried re-drawing several CC64=0 to higher values in the PRV, and then changing all of them to CC64 =5 in one of my projects, and didn't encounter an problems. And I've not seen a problem with my RD-700NX which sends continuous pedal values. I would say your issue is either synth-specific or you're barking up the wrong tree that it's even related to the controllers.
 
Is it while you're entering the controllers or during playback that you're having problems? If the latter, you can rule out the non-zero sustain controllers by using Process > Find Change to set everything below 64 to zero.

It might be something else.    The lockups have happened during long work sessions with a large number of starts, stops, changes of Now times.    But only in (I believe --- like any unexpected problem I didn't keep track until it happened) small projects (chorus and piano, all midi) with sustain pedal for three piano tracks.  
 
Always on 'play', not during entering the values.   And not at the beginning of play necessarily.    Also, painfully, caused audio noise, my least favorite thing for my tired ears.   Also I very rarely change anything while a project is playing .. exception might be some tempo drawing, but this particular project had a stable tempo that I did not change. 

Since changing my project to ensure all CC64 values are 0 rather than just a low number less than 64, I have had no lockups, no startling CPU usage.  
 
Might be worth a bug report if confirmed.  And perhaps a feature request: it is impossible to "draw" a 0 controller value in the PRV controller pain.
 

I use CC64 extensively, usually with all events being non-zero.
 
Can't recall a single problem with this

williamcopper
It might be something else.    The lockups have happened during long work sessions with a large number of starts, stops, changes of Now times.    But only in (I believe --- like any unexpected problem I didn't keep track until it happened) small projects (chorus and piano, all midi) with sustain pedal for three piano tracks.  
 
Always on 'play', not during entering the values.   And not at the beginning of play necessarily.    Also, painfully, caused audio noise, my least favorite thing for my tired ears.   Also I very rarely change anything while a project is playing .. exception might be some tempo drawing, but this particular project had a stable tempo that I did not change. 

I wouldn't expect any single MIDI event to cause something like this (especially since you are suspecting non 0 values and why should a particulr CC be any different to others, they are all just numbers send to a channel) ... there's most likely something else going on (buffer filling up after long sessions, MIDI loop???) or even more likely something happening to your audio interface (as you also report audio noise) ...

I accidentally left in a CC64= 3 recently; got the freeze again.     I'm getting more and more sure it's something to do with the audio engine trying to sustain notes according to a CC64 value. 
 
This happens after an hour or so of work, with many starts and stops, so it is not the kind of thing that happens immediately.   The CPU at 100% can not be stopped -- you have to exit Sonar.  
 
Possible additional factors:  3 midi tracks going to 3 different Kontakt channels, CC64 values different in the three tracks, but the 3 Kontakt channels all going to the same single output track.    Midi lookback preference enabled; zero controllers on stop disabled.
 
The latest freeze happened not during playback, but when I dragged a note (in the track with a CC64 = 3) to a new pitch in the PRV.  (edit)  Opening the same project, dragging the same pitch -- I can hear that the sustain pedal effect is ON, though it should not be.    Is there any kind of lookback during the sounding of a note during note entry or modification?   
 

More details, same project:   during complete playback just now, I watched the CPU meter in Performance Module get higher and higher -- when playback got to the point where I added CC64 = 0 suddently the CPU meter moved back to its normal nearly zero position.  
 
On the next playback, the CPU meter began and remained at the normal very low level.    Definitely related to CC64, imo.
 

I actually had something similar last night: 2 lock ups / crashes when recording piano as MIDI track while working the sustain pedal heavily.
 
Have not seen that before, but it happend twice on the same project within a short time. So I take back what I said earlier - the crashes were definitely while recording MIDI @ low ASIO buffer settings and high audio track count / relatively high load (but that's what I have always done before).

Definitely a bug, it's happening repeatedly.      Using "reset controller to zero on stop" in preferences does seem to eliminate the problem, but I don't like that option because it then makes other controllers zero out, so that restart in the middle of a project becomes prone to wrong sounds.