Replying to Final Cut Lagging

i did some filming with the new go pro hd hero 2 and then converted the files so they are able to work in final cut express. After I imported the clips to fce, playback was smooth, but trying to edit has been horrible. When I drag the clip into the sequence, i have to render it for like 45 minutes and the clip is only 5 seconds long. Also dragging the clip or the marker in the timeline takes forever. Everything in my program slows down when i use the footage. What should i do?