Hi all! Add to the long, long list of bugginess I've experienced with X2 this new one.

I have lots and lots of envelopes drawn on my projects- I work with lots of samples and softsynths whose properties change over time. Sometimes, while working with the projects, I'll start playing back a track and Sonar won't follow some or all of the envelopes! This seems to happen without obvious cause- I'll make a change such as moving a Volume slider, and that'll set it off. It affects envelopes for softsynths, volumes, send levels, and various other parameters.

The problem usually repairs itself when I close and reopen Sonar, but lately not even rebooting my machine has fixed the issue. 

Any ideas??? :/

You might be in Offset Mode.
 
http://www.cakewalk.com/Documentation/default.aspx?Doc=SONAR%20X3&Lang=EN&Req=Automation.13.html
 

Good idea to check if your in offset mode.  Otherwise, I've seen this happen often in X2a.  Sometimes it seems to be a display issue.  The track might actually be following the envelope, but the control (knob, slider, meter, etc) does not reflect changes during playback. 
 
It's definitely buggy, as sometimes it works, sometimes it does not, for the same envelope.  I found in a few cases that collapsing the Automation Lanes and re-expanding resolves it temporarily.  See if that helps you.

Presumably the tracks in question are set to Read automation?

I know that there's a reproducible bug where you create midi envelopes and then render/bounce/whatever in real time and Sonar ignores the envelopes. That's a huge problem... it's a major feature that just flat out doesn't work. It's been confirmed by Cakewalk in X2 and here we are in X3 and it's still not fixed, never been addressed. Last time I emailed (politely) expressing my disappointment that a major feature remains unusable in X3 and asking when (or if?) they planned on fixing it,  I didn't even get a reply. Very frustrating.

I haven't bumped into that bug as much as I use envelopes. Do you know the bug number?

Well, I'm disappointed too that it hasn't been fixed in X3.  How about X3c?  I know I've submitted a bug report on this issue as well for X2a.  I don't recall my case number, but I'm sure there is more than one out there.
 
I posted a big X2 vs. X3 issues question as it will determine whether or not it's worth it to upgrade at this time.  This was one of my questions.