Windows 7 Self-Lockout Feature: "User Profile Service Failed to Load"

Being locked out of one's own computer is a proven precursor to madness. It's now happened to me several times on several different machines -- both under Vista x64 and now twice under Win7 x64. Windows is restarted, and either user desktop fails to restore, or, on this occasion, Windows refuses to log in the user, because "User Profile Service Failed to Load." When this happens, you'll be left dumbfounded at the Windows login screen. 

From what I've seen, chances are good that you didn't do anything wrong.

There was a recent set of Windows Updates in the last 48 hours that I am tempted to blame for this, but there's no proven connection.

Some tips:

• If the "locked-out" account is the only account on the machine, you will have to create 1-2 new ones, depending on how you decide to try to recover your data.
• It's unlikely that a heavily used account (lots of customization and licensed software installed) will get back 100%. Prepare expectations.
• You'll need to boot into safe mode to gain control long enough to create a new account if one isn't already available.
• Remember that if F8 during startup to get to Windows safe mode option isn't working, it could be because Windows won't recognize F8 over USB or wireless. Use a regular wired keyboard or the main keyboard on a laptop. 

Microsoft suggests several possible solutions to correct "a corrupted user profile." The first option is to restart -- which of course had been tried several times before reading their tip. Then the FixIt solution was attempted, after creating a new admin account in Safe Mode. No love there, either. 

That left a third option. This is a messy process of creating a third account from which to copy profile data from the stranded profile to a new one. That is, a User3 is needed to copy stranded User1 data to a new User2. The details are in the Microsoft prescription. However, you'll be mildly unsatisfied with the results, depending on the situation. In my example, the user profile directory was 3.6GB which had to be copied to User2's directories. The "corrupted profile" files and registry remnants remain to be disposed of. 

How do things work out with new User2? While most apps will launch, many will have to be reauthorized, which took several hours in my case. Further, many had lost settings and these had to be relearned, rediscovered and painstakingly restored.

A quick search for Windows or third party backup/restore processes specifically addressing a Windows user profile didn't turn up anything specific; the goal would be to address this specific failure which it's fairly clear is likely to recur. Ideally, one would want a backup/restore solution that addresses any registry changes as well as the files associated with %USERPROFILE%.

I am fairly certain that users aren't doing anything especially unusual when the "corruption" occurs. I fully expect that it will recur unless the underlying causes are addressed.