Change starting frame of motion tracks I have a clip that needs additional frames to be inserted at the beginning. I've tried copying and pasting the motion tracks, but they always start at the same frame. I've also tried to edit in the IPO editor but they can only be slid up and down.

Is this possible?
It sounds like you want to use blender's Video Sequence Editor.

http://wiki.blender.org/index.php/Doc:2.6/Manual/Sequencer/Usage

You will create a Movie or Image strip from your source clip.  You will then drag it to the right to open up some time at the beginning.  You can then add a strip for the added frames (whether they are an image sequence, movie clip, title card image, or solid color) in that space.