Can you tell us what model of camcorder this video came from and, if it shoots in more than one mode, which mode it was shot in?
Also does your computer have a single, dual-core or quad core processor? If a single-core processor, it likely doesn't have nearly enough power to edit this video. In fact, when editing hi-def, a quad-core processor is usually recommended.
For getting up to speed with PrE, this ARTICLE lists some useful resources. I strongly recommend that one start with Steve Grisetti's Basic Training Series.
You mention K-Lite. Did you install the FFDShow module that is included? That has been known to cause no end to problems with Adobe video-editing software.
The clips didn't come from a camcorder. They were professionally authored clips that were given to me.
My processor is dual core.
Would PE simply shut down if there wasn't enough processor power?
Read Bill Hunt on a file type as WRAPPER http://forums.adobe.com/thread/440037?tstart=0
What is a CODEC... a Primer http://forums.adobe.com/thread/546811?tstart=0
What CODEC is INSIDE that file? http://forums.adobe.com/thread/440037?tstart=0
Report back with the codec details of your file, use the programs below
For PC http://www.headbands.com/gspot/ or http://mediainfo.sourceforge.net/en
For Mac http://mediainfo.massanti.com/
Once you know exactly what it is you are editing, report back with that information... and your project setting, and if there is a red line above the video in the timeline, which indicates a mismatch between video and project