Ok, 1st off, please post smaller pics, the moderators may not like this much.
2nd, I just did the same thing you did - import an iMovie video - on my MBP and got similar memory results (in fact it used less - right at 32 mb). I too have 1 GB of RAM.
However, my CPU usage was at 7%, whereas your's is at 80%. Even adjusting for the MBP's superior processor, that seems unlikely. What PB are you using?