I was looking at a Windows 7 machine that whenever a new domain user who had never logged onto a machine before got the following error message:
The User Profile Service service failed the logon. User profile cannot be loaded.
Now in this case there was an existing Microsoft KB article for this located here http://support.microsoft.com/kb/947215
However in this case the cause was a different issue. I had logged successfully onto the machine as a local Administrator and confirmed no profiles already existed on the machine.
Log Event would show a more complete error message
Only part of a ReadProcessMemory or WriteProcessMemory request was completed.
It turned out it was due to an Internet Explorer upgrade with Send Feedback option enabled, which created some .SQM files with wrong permissions. In the end I deleted the whole C:\Users\Default\AppData\Local\Microsoft\Windows\Temporary Internet Files folder and the issue went away. Tip: one can use ProcMon to debug such issues.