I am having a problem with the audio sync when I render a project. I am just creating a simple 2 minute single shot, with a few edits project with an audio mp3 (music video) and the audio sync seems fine in preview mode... when I render it seems to be a bit off...

Anyone know a solution?

I reported a bug with MP3s a while ago, see report here:

http://www.kdenlive.org/mantis/view.php?id=2160

Solved by converting to WAV first, then use that in your project.

See if the bug report matches your circumstance and comment if you can add any more info