Can't change lock screen on windows 8.1

If you have some specific data applicable to this exact problem, I'd love to hear that specific relevant data.  In the beta, we (my team) had a bug wherein ACLs were incorrectly migrated in one particular scenario, causing a very similar lack of functionality.  An educated guess as to this problem would indicate that ACLs are probably being reset by the upgrade path.  But without a machine to look at in person, I can only hand wave over the problem.  Clearly the machine should not hit this problem and if it does hit this problem it should recover as cleanly as possible.  Both parts of that statement are not being met right now, and I apologize for that.  This is a bug, and I need more data in person to work upon it.  Malware is not involved here.

There are many thousands or millions or hours of testing involved previous to release.  It does not and can not catch everything: that's part of the reality of computing.  This is a legitimate technical issue probably caused by one particular code path.  Please please do not distract or confuse users by bringing up non-germane data.  If you have specific data that correlates to this problem, I'm all ears.  But until you have specific data, I, as someone who has personally actively fought against malware and helped shut down botnets, would ask you to stay relevant to the topic at hand which is solely ACL corruption on a folder that malware does not have access to.

Hi!  I'm the developer at Microsoft in charge of this code area in question.  I am pretty certain that they have not been hacked and that malware is not in play.  This problem of theirs should likely be a byproduct of corruption of file system ACLs for some unknown reason, most probably a timing issue during access/update.

Could you clarify the exact reason why you believe malware is a possible question here?  I read your posts as generally speaking from a position of paranoia as opposed to a technical grounding.  Could you clarify the technical grounds for making the statements you're making, specifically with regards to what malware would have had this effect upon a system?

The lock screen image set failure is interesting: if I can get a machine in Redmond to look at with this problem, I'd be happy to investigate and figure out how the code can work around this issue.  For remote users, creating a new user profile (or recreating one) should probably fix this up.

MICROSOFT SUPPORT:

Is Kevin DeCarlo's assertion true? Is this really an issue with computer intrusion? I'm somewhat skeptical, so I'd like confirmation. Or is there a diagnostic I can run to confirm?

There are many other threads in this forum about issues with the Windows 8.1 lock screen not changing. On one of them someone did a fresh install of Windows, which didn't help.

So, how do we fix this? If you don't have a fix, please let us know the timeline for having one.