Unrelated error messages, their means, and solutions.
Kali Linux Live USB Flash drive
You are getting a segmentation fault error (signal 11) in X.Org when you try to boot from your USB flash drive:
Fatal server error: Caught signal 11 (Segmentation fault). Server aborting. Please consult The X.Org Foundation support at http://wiki.x.org for help Please also check the log file at "/var/log/Xorg.0.log" for additional information. Server terminated with error (1). Closing log file.
Did you use unetbooin' to burn the ISO file to a USB Flash Drive? That's the cause of this error. The problem is that unetbootin isn't perfect and makes some assumptions. It actually takes apart the ISO and makes extensive changes (including changes to partitions and the filesystem type) before writing to a USB flash drive. The KALI Linux Live ISO is actually designed for copying directly. You do not need to use any tool to modify it to copy to a USB flash drive. Just use dd to copy the ISO to the device (assuming your SUB flash device is '/dev/sdb'!):
dd if=kali.iso of=/dev/sdb bs=512k