This problem occured on 3 different servers :
There is a Program document to restart the server at 6 am.
None of them worked properly.
Apart from this log message :
30/09/2010 06:00:32 Running Program document for ‘nserver -c “restart server”’
there is nothing to say that something happened.
But there were up to 4 nserver.exe on the machines running high cpu.
I had to restart all 3 servers.
Never see that before.
8.5.2 has been installed for 2 weeks now.
Any comment welcome.
NB : yesterday came some Windows updates…
Siverlight 
and Windows Server 2003 update (KB2158563) which has to do with summer time.
There was no request to restart the server, and that might be it !!
Jean-Pierre
France