I can only think of several reasons that this might be happening.
* The wood you are cutting is splintery that is it splinters easily
* The wood is very brittle - like old cedar tends to be.
* The blade is too aggressive for the wood thickness
* your saw might not be tracking perfectly up and down and side to side
* the blade is upside down
Solutions to most of these are fairly easy.
* Tape the work to be cut
* make sure the blade has been installed correctly
* try a practice cut to see if your saw is tracking properly of not.
DW