ProTools 8 offers the option to open a session without the plug-ins active – COOL! This solved my problem. I spent a few hours last night tracking a song and when I came back this morning and tried to open the session, ProTools froze once the session appeared on the screen.
I tried opening other sessions and they opened without a problem. I searched for a way to open a session file without the plugins and found it. Use a shortcut for opening your session file - in the “open session” window or if in the “recent sessions” area, shift+click on the session file name or “open” button and the session will open with all plug-ins inactive.

Thanks. that really helped….