I'm resurrecting this because I've finally been able to narrow down what's happening when desktop icons re-arrange themselves even though auto-arrange icons is turned off. I've been paying more attention to what has been done when this occurs and I can now cause this issue to reliability occur. This is what I've discovered:

1. When you remain signed in and sleep the computer, and then wake it up, the icons remain where you put them. The same goes for shutting down and restarting if only one user is dong this.
2. When you remain signed in and sleep the computer, then another user wakes it up, signs in, then signs out, when you re-sign into your account the icons have moved.

For anyone else with this issue, can you verify my observations?