What version of Premiere Elements are you using and on what computer operating system is it running?
You have not given us enough information with which to help you. For starters, besides version and computer operating system, please supply
1. Project Preset
2. Properties of Source Media
3. Details of the projects save/close.
Also please review the Adobe document on troubleshooting damaged projects.
After that we can customize the troubleshooting strategy to your particular circumstances.
Any questions or need clarification, please ask.
Looking forward to your follow up.