imovie slow?

Okay so this is almost a follow up from my last question. I haven't used I movie for a while (2-3months) and now it has to reload every 45 seconds or so and at sometimes just completely quit itself..

When I first got my macbook pro this would never happen. I have a feeling its something to do with the memory? I got this computer late 2011

Any advice? Someone with the same problem?

Also I WAS able to import the videos to my macbook pro from a Sony HDR-CX210 Handycam

I imported and that was good it worked. But when I started to put clips together, iMovie had told me I had to refit the frame rate to 30 fps -NTSC

What does that mean because now my clips are zoomed in more and cannot see the big picture

What can I do for the next time I run into this?