Preview stops at 30 minutes

[Eltrian Artiiran]

-64 bit
-Err, latest Mac operating system, whatever that is called
-Installation Method: Um, the normal way? I don't know how else to do it
-Version: I downloaded it less than a week ago, so I figure I have the latest
-I don't know what BZR Revision, melt, and FFmpeg are, so I can't include that information.

I'm trying to edit a video that's over an hour long, and to edit it properly, I need to look through the video to see what I need to cut out, and where would be the best place to split it in half to be two videos.

However, the preview always stops at the 30 minute mark. I tried researching, but the only thing I got was telling me to increase cache size, which did nothing.

Any help would be greatly appreciated!