Maybe SBS is doing something funky with the ACPI restart?
I don't suppose you know if 2003 or Windows 7 does the same thing; do you?
What is the beep sequence that it gives you? 1-5-4-4?
Beep sequence is hard to say for sure as it is fast.. but yours sounds about right.. and both sound the same (Power Cycling where it will start) or Reboot (where it will not start)
no idea on Win7 or 2003.. only have 1 machine and it is my main mail server/ storage server
In theory, SBS 2011 is the same as 2008 R2, since it's the same kernel - but I've seen odd behavior like this before. It doesn't usually interfere with production, but unpredictable results sometimes occur with the SBS family.