Mac Won't Boot. Help needed
To fix this try the following:


boot to internet recovery mode by pressing cmdaltR immediately after the start-up chime. Depending on your internet connection the boot process may take several dozen minutes.
open Disk Utility, choose your main volume, verify and repair it if necessary


if you had to repair errors just repeat the step to recheck that all errors are gone
reboot to your main drive
if the problem persists boot to single user mode by pressing cmdS after the start-up chime to circumvent the lockout.
after booting is done just enter 'exit' at the prompt to start to the common Aqua interface.
download Onyx or Yosemite Cache Cleaner
start Onyx
clean system/user caches


or start Yosemite Cache Cleaner
clean system/user caches



** "System" is the name of the start volume in my VM. Your volume name may be different.
restart your Mac