It's impossible to say without knowing which version of the program you're using, what operating system you're using and if it's fully updated, how fast your processor is, how much RAM you have, how much free, defragmented space is on your hard drive and what kind of camcorder your video is coming from.
It's also helpful to know what exactly you're doing when this error occurs.
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This ARTICLE will give you tips on the types of information that will help others help you most efficiently and effectively.
Good luck, and we'll be looking for the info to help you solve the issue.
What is your operating system ? Are you using Premiere Elements 8.0 ? What action do you perform when you get this error? What type of media do you have in your clip?
You'll need to give more details before anyone can help you out with this!!