We have since updated sk163461 to make the steps more clear (which ISO file we tested, example of edits) and recommend use of Rufus instead of Unetbootin to produce more consistent results with USB stick creation.
The behavior reported by the original poster (freeze after boot menu) will happen if the files on the USB stick as indicated in the SK are not modified in the correct way. The purpose of step 2 of sk163461 is to redirect the kernel text output to the serial console port on a Check Point appliance after the boot menu, since those appliances do not have any standard VGA video output.
If the serial console output freezes here, the kernel is probably not outputting to the correct RS232 serial port on the appliance. Removing "rhgb" and "quiet" will disable the CentOS graphical boot, console=/dev/ttyS0,9600 will output to the first RS232 serial port on the appliance (serial console port).
To answer another question in this thread, the procedure in the SK will still work on a VM however you can omit step 2 which requires editing of isolinux.cfg, since in this case the VM does have standard VGA video output.