I don't know what button I pressed which started this behavior, but it's driving me nuts.
 
I have multiple tracks, each of which have multiple envelopes.  When showing the envelopes for a given track, all the envelope lanes for other tracks collapse.  The envelope button for each track is "grayed out" as well.  This means that I have to click the envelope button for each track to modify its envelopes, significantly slowing down production.  I often write a passage, then modify the envelopes for multiple tracks all at once before moving on.  Please tell me what button I hit that enabled this "feature," and how to turn it off!
 
 

I'm not sure what you did to change things and I can't replicate.  But I can see and edit the envelopes in multiple tracks better when I display them in-line within the track (not in the separate parallel pane below).  Directly under the name of the track, click on the drop-down button that says "Clips" and switch is to "Automation>Volume" Or "Clip Envelope>Volume" (or "Pan" or whatever you're working on).  Then the envelope appears along with your waveform or your MIDI dots and dashes.  The envelopes are bigger and you're not messiing around with those tiny automation lanes below the track which are sometime hard to grab and enlarge.  You can see several tracks at a time at a decent size.

Kind of sounds like Auto Track Zoom (Shift + Z) is activated?

I have had the same sort of behavior. Controller lanes show when the project is saved and closed. Reopen the project, the automation tracks are not there and greyed out on the track. I click the automation track, click the write automation button and all automation tracks in the project return to the original state.
I just happened to stumble on this workaround out of sheer frustration and haven't heard anyone else complain until now. Glad to know it wasn't just my system!

Thanks for the help guys.  For better or for worse, I like having the automation lanes below the track data itself as opposed to on top of it.  I think Shift+Z was the source of the problem, as that seems to allow me to expand the automation lanes for multiple tracks again without each one collapsing when I expand the lanes for a given track.  Sidroe, thanks for your help as well, as it gives me more insight and may help me correct these types of issues in the future.  I've never experienced this in 15 years of working in Sonar... which I suppose is no longer called Sonar.
 
Anyway, a few dozen clicks have re-expanded the automation lanes for my tracks so I'm back in business.  Thanks all!