[Steve Rauscher]

I am also a Premiere Pro user on the Mac platform experiencing this very same problem. My videos are captured via Hauppauge HD PVR 2 (video game footage) at no more than 30 fps. The raw files are captured in the very strange .m2ts filetype, but I transcode them to H264 .mp4’s before introducing them to Premiere. It’s only after pre-rendering that they become slow motion and have the ending cut off. I have not tried exporting the result to a new .mp4 as the OP did, because I simply have to edit so much of these clips to make them viewable.

I will say that these problems were not occurring for me before I switched my operating system to Apple’s new Mavericks, so I’m prepared to accept that that is the issue.