What version of Premiere Elements are you using and on what computer operating system is it running?
What are the properties of what you are taking to the Timeline of the project....for video, video and audio compression, frame size, frame rate, interlaced or progressive, file extension, pixel aspect ratio....for photos, how many and what pixel dimensions?
Based on the properties of the source media, what have you or the program set as the project preset? If you do not know, please check Edit Menu/Project Settings, General, Editing Mode, Timebase, Frame Size, etc.
What is a description of your computer resources...installed and available RAM, free hard drive space, etc.?
Have you gotten to export, either to file saved to computer hard drive or burn to disc? What is your intended export for your Timeline?
The usual drill questions:
1. Do you have the latest version of QuickTime installed on your computer with Premiere Elements?
2. Are you running the program as Run As Administrator or from a User Account with Administrative Privileges?
3. Is your video card driver up to date according to the web site of the manufacturer of the video card?
Please answer the above and then we can decide what next. Do not hesitate to ask for clarification if anything above is not clear to you. We will re-write to make the points clearer if necessary.