Premiere Elements 12 on what computer operating system?
Are you just starting to work with this version - new project but long time user or new project and new user?
Have you updated 12 to 12.1 yet using as opened project's Help Menu/Updates?
Please verify - "start a new project" means that you cannot open Premiere Elements 12 to the Expert or Quick workspace when you select Video Editor/New Project? I want to distinguish that from problems when you start a new project and have problems importing your files to the Timeline.
Does the problem exist if you disable the antivirus and firewalls?
Do you have the latest version of QuickTime 7 installed on your computer along with Premiere Elements? Are you running the program from a user account with administrative privileges?
Are you working with an Internet connection?
Is your video card/graphics card driver version up to date according to the manufacturer of the card?
What are your computer resources? If you go to Edit Menu/Preferences/Scratch Disks where are the scratch disks pointed and how much free hard drive space is there at those locations?
Let us start here and then decide what next based on the details in your reply. Any questions or need clarification, please do not hesitate to ask.