Trying to update MacBook Pro, OS X. Yosemite from 10.10.2 to 10.10.3 (Recovery Update 1.0). After downloading the update, the Mac flips to automatically restarts and launches "Software UpdateLauncher." The Mac doesn't respond to any command.

Question

Once I download the update (OS X Yosemite, 10.10.3, Recovery Update 1.0), after the system automatically restarts, the launch page is "Software Update Launcher." Looks like a typical menu bar, and the rest of the screen is blank. None of the commands work, though. Even trying to shut down via the menu doesn't work, and the only way to get past the page is a hard shutdown and restart. Once restarting, everything works as it should EXCEPT the update did not install.
This same thing happened with the previous Yosemite update, and I wound up taking the laptop to the Genius bar where no one was familiar with the error. After running virtually every diagnostic, removing a suspected out of date security application (Intego), the decision was to restore the Mac to factory pristine state. OUCH.
We have a MacBook Air, which has the same OS version and security and other third party software as the Pro, and it has not experienced this problem.
I've made another appointment at the Genius Bar, but I sure as heck don't relish the idea of having to wipe my Pro clean again and having to start all over. Time Machine backups are great, but they don't restore my system as though nothing happened.
Any suggestions or proven remedies??
Thanks.

Answer 1

Another thing that is probably relevant now that I think of it:
I forgot that the xcode_3.2.6_and_ios_sdk_4.3.dmg file would not open on it's own. It would get all the way through the verification process and then display "invalid checksum". I had selected Skip to bypass the verification process in the hopes that it would install anyways. Just ejected it and tried to verify it again, same "invalid checksum" error.
I've looked for solutions online and everybody just says to keep downloading it/have a wired connection and to use Safari... I've downloaded the thing 5 times now meeting both of those requirements and the exact same issue occurs every time.