I don't use iMovie, but I highly recommend FilmRedux to compress your file. It's the open source version of VisualHub, an amazing app that was the standard for video conversion.
Download it here. http://www.transcoder-redux.com/transcoder-redux.dmg.zip
Safari crashed because it was trying to put a lock on and move a 2 gig file. Sometimes Safari will beach ball for so long that it thinks it has crashed and the OS kills the app.
"Adam, you'd love this. I hit Liz in the box with a 10 pound block of cheese." - Garvey
"Flushable toddler wipes rule! They're like a bidet on a napkin." - Steph