I am strictly an Elements Windows user, but let us try to determine if there are some non Mac El Capitan reasons for your project not to open.
Does the project workspace open and then crashes before you can begin your edits or does the program crash just trying to open to the project?
If trying to open and edit a saved closed project is the problem, what happens if you try to open a new project? How far do you get with that?
Have you completed any projects prior to yesterday?
Have you gone through the usual check list -
a. Latest version of QuickTime installed on your computer
b. Running program as administrator (from user account with administrative privileges)
c. Any antivirus and firewalls activities that could be interfering
d. Video card/graphic card driver version up to date
e. What was the last activity in the project that you performed before the save close?
f. Do you work with AutoSave feature On? If so, can any of the AutoSaves for yesterday's project be opened?
To answer your questions, it crashes regardless of whether I try to start it with a new or existing project. I have quit all other applications and re-booted my Mac as well as re-install Premiere Elements. I do work with autosave and it did autosave a new project yesterday. Last thing I did was to save that project with a real name. Then I Quit the application normally. There have been no hardware changes or op sys updates in the interim.
Ahh, but I think you did help me get back up! I went to the folders containing previous projects and if I selected one and clicked "Open With" Premiere Elements, it now seems to be up! I will check to see if it actually works - it's been very problematic with El Capitan anyway, so I may still have to find an alternative..........
Thanks for the update with signs of hope for program/projects recovery.
Also, determine if this applies to you....after the project has been saved closed be careful with moving, deleting, renaming of files and folders that went into the project. When you import originals into the project all you get are copies of the originals. But, the project copies need to trace back to the originals where they were and named when first imported into the project.
Please update us on your progress as your schedule permits.