Cause: getC, setC, setActionC, setActionB or setM called with too large argument.
Molecule cells hang out of the applet, some inner rows intertwine.
Applet size too small.
There are some rows of labels, buttons, or checkboxes in a cell between the molecule, and their total height is bigger than the molecule height you specified.
Solution: increase molecule height, decrease the font size, or reduce the number of rows per cell.