Nobody will be able to even guess at how to solve your issue without a lot more information. Can you provide all the detail?
Bill is right.
What processor are you using and with how much RAM?
What operating system are you using? Have you ensured you have Quicktime 7, per the program's requirements?
What model of camcorder is your video coming from and what format and resolution is the video?
Under the Premiere Elements Edit menu, what settings are listed under your Project Settings?