I'm not sure about this so I don't want to make the edit myself but the 
sample cfg file in this tutorial:

http://www.ros.org/wiki/dynamic_reconfigure/Tutorials/HowToWriteYourFirstCfgFile

might be missing the line:

#!/usr/bin/env python

at the beginning.  At least, rosmake fails with a syntax error without 
it but builds fine when I put it in.

--patrick