What is the source of your Premiere Elements 12 Mac - Adobe download or from installation disc purchased in box packaging from authorized reseller?
There are many questions to be asked:
1. When do these crashes occur - you are importing, editing, or exporting?
2. What are you or the project setting as the project preset for your project? See Edit Menu/Project Settings/General and the readings for Editing Mode, Timebase, Frame Size, and Pixel Aspect Ratio? And, what are the properties of your source media whose properties should match the project preset?
What is the brand/model/settings for the camera that recorded you video? What is the duration of your Timeline when the crash occurs?
3. Do you have the latest version of QuickTime installed on your computer?
4. Are you running the program as an Administrator?
5. Is your video card/graphics card up to date according to the web site of the manufacturer of the card?
6. What are your computer resources?
We can continue with the exchange of troubleshooting information.
But, you can also contact Adobe at its Adobe Chat to work through Downloading, Installing, and Setting Up topic. It, unlike us, might offer you some remote control of your computer troubleshooting.
Please let us know the outcome.