I have an incredibly annoying problem, mainly on my White Macbook 13", but also sometimes on my main iMac (Aluminium 2011, I think) both running Snow Leopard, in that when issuing a Shutdown command from the main login screen, the machine will not actually shutdown, but restart. This will also happen, but less often when a Shutdown is issued from the Apple Menu and it's even happened once or twice when issued in Terminal (for goodness sakes' - the *command* line Apple - how can you get *that* wrong?).
It's most frequent, & annoying manifestation is when I hook into my Macbook from my main Mac via MobileMe to shut it down. I hit Shutdown and at least half the time it will Restart. But, I don't have to use MobileMe to make it happen. It will also restart if I'm actually on the Macbook's login screen and issue the command there.
What is going on? This is a basic, fundamental system operation that a user wants (& expects) the system to *obey* - no ifs & no buts about it. Because this has happened on both my machines, I'm posting it in Mac OSX. It didn't happen on Leopard, I'm sure.