I am also experiencing this problem.
Avid can't seem to help me.
It seems that it's not so much if I'm working fast.
From what I can tell, I start a new session, work in it, everything is fine.
Then I if I close the session and reopen it, some randomly chosen MIDI region (or a few even) creates the crash. It crashes on the first click even, not the double click. Spinning ball.
A workaround, a terribly inconvenient one, is to select the area around the region and consolidate it. That SEEMS to keep the problem at bay, but it's a real hassle.
With a midi track count up near the track limit, I either have to wait for the crash to find the culprit(s) , or just consolidate everything and then deal with a zillion regions, most of them blank. Can't offer a real solution but I've been looking for weeks for even someone else with the same nightmarish problem and it looks like you and I are the only two.
I write music for film and TV and this is really slowing me down.
Is it a graphical problem? A random, unconsolidated MIDI region being clicked or half-clicked, causes it. It's crazy.
It started when I upgraded my OS. I did a full reinstall and now I'm back to the old OS, pretty much a clean install. Problem was still there.
and yes I've trashed the prefs. Believe me. Trashed em good.