What version of Premiere Elements and what computer is involved?
Is this a new install? Is this "it worked before but not now" or "it never worked before"?
Troubleshooting plans depend on details of the situation.
a. Does problem exist with and without the antivirus and firewalls disabled?
b. Do you have the latest version of QuickTime installed on your computer along with Premiere Elements, and are you running the programs from a user account with administrative privileges?
c. Is your video card/graphics card driver version up to date according to the web site of the manufacturer of the card or the manufacturer of the computer?
And, there are more questions which can be version specific so we shall wait for details in your reply.
Any questions or need clarification, please do not hesitate to ask.