help with physics

i have made a level and it normaly plays allright , but somtimes the main charicter just falls through the ground, when this happens the console window says: dropping physics rate,
do you guys know how to stop this?

Again sounds like centre of object being in the wrong place or bounding box being wrong size… for the main character Editing Panel(F9) / Mesh / ‘Centre New’ button

thanks:evilgrin::evilgrin: