Nothing is perfect and no matter how carefully you manage your system, sometimes you’ll find a session you are trying to open just won’t play nice. Pro Tools has had its moments in terms of stability but often Pro Tools is getting the blame for a crash caused by a plug-in.
If you hold down Shift while opening a Pro Tools session the session will open with all its plug-ins inactive. Once in the session you can set about identifying which plug-in is causing the problem. In a big session I find using CMD+Option+Ctrl/Start+Alt+Ctrl to activate plug-ins one slot at a time across all tracks speeds things up significantly if I’m trying to identify issues.
This is a life-saver when trying to resurrect a reluctant session.