Major iMovie problems... how to reinstall?

I have had some problems with flaky behavior of iMovie during importing before but this problem today is off the scale.

I had 64g of HD video on my camera & started importing. I've imported many times from the camera so no hassles there.

About 1/4 of the way through the import my Mac hung. All apps froze. Now I don't know if iMovie caused this as I was also doing other things at the time.

Anyway I had to force the machine to shut. Restarted & some of the footage is there in iMovie so remounted the camera etc & now iMovie won't see any of the remaining footage & it is being really weird in how it opens the import window, it behaves like the import window is open but there is no import window & then when I can get an import window there's no footage visible to import.

Naturally I freaked thinking I'd lost the footage so I looked into the files inside the packages on the memory card & they are all there and I have in-fact imported onto my other Mac with no problems.

So I'm thinking something has gone seriously wrong with my install of iMovie.

Can someone tell me how to reinstall iMovie so it will still find all my footage etc & not lose projects etc? And the best way to get iMovie events from one machine to another?

Thanks in advance.

p.s. - iMovie 9.0.9 on OS 10.8.5