The last line in your .out file shows the error. Compare it with the corresponding line in the .cmp file to see what is different.
The out column should be one of the a, b, c or d input values. The .cmp file will tell you which input should be selected. The .out file will tell you which input your mux selected.
From your description of your mux I suspect that you will find that b and d inputs are being incorrectly selected. It sounds like they are not connected to the correct Mux16 inputs.
Email me directly if you want more explicit help. (Become a registered member of the group and you can use More>Reply to Author.)
--Mark