I have recently got a strange issue that only affects one user (me!) on a Shuttle SFF PC running Windows 7 Professional. If,when LOGGED in as that user, I attempt to log off, hibernate or restart the PC, it shuts down instead (a hard shutdown). It is exactly as if I had selected 'Shut down' from the Start menu. This happens whether I do it from the Start Menu, or from a command PROMPT using shutdown.exe, also when a newly installed piece of software or Windows update asks to reboot the computer. I have to use the power button on the PC case front panel to bring the computer back up. If I want to hibernate or restart I can switch user and do it from another login.

I do not think it is a hardware issue because it does NOT happen:

When logged in as any of the other 3 users.
In the boot menu of a Grub4DOS bootable pen drive (can select restart and get a restart)
When running a Slax Linux LIVE CD (LIKEWISE can restart)

Any ideas? I have checked HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Shutdown and there are the 2 DWORDs I expect, LogoffSetting (=0) and ShutdownSetting (=3). I am not running Norton Antivirus!