Problem in the firmware compilation

I have the source code of Netgear 1.1.11_6.0.36.

The problem is that whenver i compile its code and get the "chk" file as output... i check that file using hexeditor and find that every output is a bit changed from the previous one. Some values in the hex editor are changed.

Moreover these compiled files are quiete different than the orignal 1.1.11_6.0.36. chk file that i downloaded from the netgear's website.

Can anyone tell me what could be the problem ..

One thing that i notice is that when the code is under the ending point of its compilation stage, when it is under:

### Create Squashfs filesystem ############

there comes a notification in my task bar that :

avc: denial