I used to create bootable USBs in the following way and it used to work perfectly fine:
sudo mount -o loop /path to iso/ /media/iso
cp -a /media/iso/. /path to usb flash drive/
sudo syslinux -s /dev/sdX
And then renaming the isolinux folder to sylinux and the isolinux.cfg file inside it to syslinux.cfg
But now when I boot from my USB, the ubuntu system boots and hangs on one screen. Everything shows up except the Installation Dialog Box where I have to click the install button.
The Ubuntu ISO was created using remastersys by the way.
And even when I tried to make the USB bootable using usb-creator-gtk, it went till 99%, asked for password to install the BootLoader and then said "Failed to install BootLoader".