You've probably recently installed the Davisville map, am I correct? That installs a matrix.osc file which doesn't work and screws up the numbers, either re-install or try and find a new matrix.osc and matrix_D.osc file from somewhere. New buses come with it, so download the Mercedes bus or something for the matrix_D.osc. But I don't know where to find a matrix.osc I'm afraid.