Segmentation faults can arise from many causes, and can be merely the final gasp of an earlier problem. Careful reading of the output log file for other warning or error messages should be your next step.

The problem could be bad input of some kind (syntax, numerical value, data file, etc.) or it could be a bug, fixed in a later CHARMM version; c43b1 is available, and the free version may meet your needs . There can be bugs that are compiler dependent, so it's often worth trying a different compiler.

Rick Venable
computational chemist