Cannot Boot after Yosemite 10.10.2 Update

I know this has been a problem for Mac users with 3rd-party SSD drives, but my 2014 Retina iMac is using an Apple-installed SSD. Here's what happened: Updated from 10.10.1 to 10.10.2 and instead of rebooting as normal the progress bar stops at less than 50% and I get the "No" icon (circle with a line through it).

I've tried just about every fix posted about this problem including:

• SMC reset

• PRAM reset

• Changed Active Directory setting

• Deleted System Configuration preferences

• Repaired Permissions and rebuilt the directory using Disk Utility and Disk Warrior

• Tried Trim Enabler kext change

• Tried Kext Utility

• Reinstalled 10.10.2 using Recovery

Nothing worked. (I did all my troubleshooting using an external HD boot system with OS 10.10.1 installed)

I just can't believe Apple would release something so trouble-filled after all the complaints about the original Yosemite.

Does anybody have a fix other than doing a complete erase and reinstall? I do not use Time Machine but have an older back-up via Super Duper.