White Screen at Boot When Attempting to Access Recovery or Select a Boot Disk

Question

Introduction
I want to share a solution for a problem I encountered that Apple technical support was unaware of (they said they would create a new kdoc when I called them to share my problem and its solution) and for which I could find no documentation online.
First, this is really a tip rather than a question, but I did leave it marked as a question in case anyone wants to earn some points by responding with a different solution to the problem I am about to describe. Additionally, I do not have a enough points to post a "Tip" so I am just starting a discussion instead.
Next, when I encountered the problem I am about to describe, I had not yet enabled a firmware password.
Finally, a massive "Thank you!" to the Great Pondini (James Pond - http://pondini.org) for helping me learn so much more interesting stuff about various OS X features and functionality (all for no charge) over the years.
Now on to why I have started this discussion...
The Problem
I recently purchased a new MacBook Pro (Core i7, SSD, etc.). After working with Setup Assistant to transfer everything from the most recent Time Machine backup of the older MBP I was replacing, applying all OS updates, and then enabling FileVault 2 and letting the requisite disk encryption process complete, I decided to I would go ahead and just proactively repair any permissions and ACLs for my user directory just in case any repair was necessary.
However, after shutting down my MBP, waiting, and then starting it up with Cmd-R being pressed while turning the MBP on, nothing would happen - I would just have a white screen with no Apple logo, no EFI login, no Recovery Console, nothing (and I waited for a very long time for something to show up). My only option was to do what I really do not like doing and that was to just power my new MBP down.
So, I tried again, this time holding down Opt while turning my computer on so as to select a disk at boot. The same problem returned.
Just to check, I once again started up while holding down the Shift key to attempt a Safe Boot. No dice.
Prior to trying all of this I made sure that I did have the Apple Recovery Partition in addition to my user partion and the EFI partition, so I did not understand why this would be happening. Why could I not boot into Recovery? Why could I not select a boot disk? And, why could I not go into Safe Boot?
To be safe, I started up and logged into my MBP as I normally would, then set my startup disk to be my Recovery USB for OS X 10.8, restarted, and verified all three partitions (and, since I had my Time Machine disk connected all three times I forced the computer to power off, I verified it as well). I then set my startup disk back to my SSD, and logged in and got online to see if anyone else had experienced this issue. After making sure I was not being crazy and using key combinations that were somehow made irrelevant, I shut my MBP down and walked away for a few minutes.
The Solution
So what solved my problem? A good 'ol reset of the NVRAM (aka/fka PRAM). If you are not familiar with how to reset the NVRAM:
Power off your Mac and go do something else for 30 seconds to a minute.
Press and hold down the Opt, Cmd, P and R buttons, and then press the power button. I have big hands and this is a one person operation for me. If you are not so "lucky", find someone to press the power button as you hold those four buttons down.
Continue holding those four buttons down through the first startup chime and then release all four of them only after the second startup chime is sounded.
So, for some reason, I had to reset the NVRAM on a brand new MBP that had been started up only once and restarted only once when I enabled FV2. Maybe something cached needed to be cleared out following the FV2 process, or maybe something funky was carried over after it was setup in the factory and shipped direct to me from China.
The moral of the story is: If you have strage issues during the startup of your Mac, just reset the NVRAM and try again. This has worked for a number of strange issues on various Macs for me in the past and proved to be useful once again on a brand new MBP that I never would have thought needed its NVRAM reset so soon into its lifecycle.
Special Note
There are two processes I always complete and recommend to others following a major software update (e.g. upgrading to a new version of OS X) and when I restore or otherwise transfer the most recent Time Machine backup to my current Mac or to a new one.
First, following a major or massive software update, go into Disk Utility, select your system and data drive(s), and then just click on "Repair Permissions" (Choosing "Verify Pemissions" will result in having to then click "Repair Permissions" if any permissions need to be repaired, so remove one click from the process).
Second, after transferring from a Time Machine backup, I like to make sure that my user directory permissions are good to go before any time is allowed for problems with those permissions to set in. If you are not familiar with the user directory permissions and ACL repair process (this process is not the same as the "Repair Permission" functionality in Disk Utility), here is how to do it:
Shutdown your Mac and wait about 30 seconds.
Press and hold down Cmd-R and then power on your Mac. Once the Apple logo with the spinning wheel shows up, release those two keys.
From within the Recovery Console, open a new Terminal session via the "Utilities" menu.
Invoke the following command (all one word, lowercase): resetpassword
In the "Reset Password" application that opens, select the disk that your user home directory is on, and then click the "Reset" button at the bottom underneath the "Reset Home Folder Permissions and ACLs" heading and wait for the process to finish. Any messages displayed can typically be safely ignored. If you want to be sure, search for information regarding any messages that you do not like.
Restart your MBP and enjoy using it.
(Note that if you have FV2 enabled, you will need your FV2 Recovery Key to actually reset your password. This is one of many reasons that I enable FV2 - anyone can startup a Mac and go into the Recovery Partition if it exists and reset a password, but having to also enter the FV2 Recovery Key adds a nice extra layer of protection. In addition to that, setting a Firmware Password makes it nearly impossible to start up from any disk other that that which is currrenlty installed in your Mac without knowing the Firmware Password - another security bonus. If someone gets ahold of your Mac, and you have FV2 enabled and an appropriately complex Firmware Password set, then them using your Mac as their own becomes a decently difficult process. It's by no means perfect computer security, but it makes it more challenging for someone to steal and use your Mac.)
If anyone has any other tips to share or additional solutions to problem I described, please discuss and share.

Answer 1

Which OS X is installed on your Mac ?
Troubleshooting advice can depend on that information.