Can't create Live USB to boot from.

[jona]

uname -rm
3.16.0-30-generic x86_64

lsb_release -drc
Description: Ubuntu 14.04.2 LTS
Release: 14.04
Codename: trusty

I am running this through Oracle VM Virtualbox on my Windows 7 machine. I have given the VM all my cores, 4GB of RAM, and installed guest additions to allow for 1080p display usage.

I tried with both of the following to try and solve through trial and error. Bug is consistent.
ubuntu-12.04.5-desktop-amd64.iso
ubuntu-14.04.2-desktop-amd64.iso

I attached build log.

What am I trying to do?:
I was originally trying to create a bootable USB that has specific software on it that will run a nodejs npm instance for a localhost server and the user can access an html link from /home/ubuntu/Desktop after automatically bypassing the Try it screen by modifying syslinux.cfg after the iso is made by mounting, copying, modifying, then repackaging into iso with the following command.

cd ~/live-cd
chmod u+w iso/isolinux/isolinux.bin
mkisofs -r -V "Ubuntu Live session" -cache-inodes -J -l -b isolinux/isolinux.bin -c isolinux/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -o livecd_ubuntu.iso iso

What do I expect?:
The resulting iso can be used with both disc AND USB media for booting purposes.

What is actual outcome?:
this iso works when burned to disc media and booted from, but booting from USB (installed by both UNetbootin on Linux AND USB installer on Windows, both don't work.) gives "No OS found" message, which quickly disappears, and my BIOS automatically boots from my primary hard drive.

Additional testing:
I have tried just installing vanilla iso downloaded from ubuntu and both boot from USB fine.
I also tried just merely loading your program, telling it I want to modify, then just choosing default-like options (only "en", only "unity", no don't remove windows stuff, and yes hybrid.) and not ever doing anything to the build when it lets me, AND also not modifying the iso at all after that.
I also tried switching to previous version and doing all types of ways to build my customization, no customization, mimicing vanilla by trying to stay as default as possible... basically anything I do through UCK does not boot from USB but boots from disc.

I am hoping very dearly that this is an oversight on my part and "oh, if you just click this." or "oh this command will fix that" can solve it.

I look forward to your cooperation in helping me in this matter. Thanks.