Looks like you will need to transcode all clips with frame rates not matching the project's frame rate:

> If the frame rate is of a clip is not compatible with your project, it
> displays in red.  You will be unable to import the clip into your
> project.  Clips with incompatible frame rates may be playable in a new
> project set to the  same frame rate as the clip.

(page 40; [User Guide][1])

You can use [ffmpeg][2], a command line tool, to transcode such clips with commands of the form

    ffmpeg -i input.mp4 -c:v libx264 -crf 8 -r 25 -c:a copy -map 0 input25.mov


  [1]: http://www.lwks.com/index.php?option=com_lwks&view=download&Itemid=206
  [2]: http://ffmpeg.zeranoe.com/builds/