- About 25-50% of cases after booting, logging into Windows produces the message "Preparing your desktop". This takes several minutes, and then you get logged into a temporary profile instead of your own, and Windows shows a notification stating "Your user profile was not loaded correctly!"
- When you check the Application section of the Windows Event Viewer under Administrative Tools, you see messages from User Profile Service with Event IDs 1502 and 1508, and contents that include: "DETAIL - The process cannot access the file because it is being used by another process." One of the events mentions specifically that the file is ntuser.dat, belonging to the profile being logged in.
I've read reports on the net that this problem can be caused by Google Updater, a program that's installed with applications such as Google Earth and Google Toolbar. Apparently, Google Updater can lock the file that contains a profile's registry, and that prevents the profile from loading correctly.
However, I have uninstalled Google Updater, and the problem has occurred again, in the exact same way, since then.