machine-id file has different id than the daemons have

[Yuri]

I have this PR in IBus 
http://code.google.com/p/ibus/issues/detail?id=789 . IBus relies on DBus 
in message passing.
On FreeBSD machine I spotted the situation when all dbus-daemon 
processes are started on Feb 17 (see note in PR), but machine-id file is 
written on Feb 21 and has different id.

My guess is that an extra instance of dbus-daemon was launched on this 
machine at the time of high load. Maybe because the communication with 
the original dbus daemon was timing out (?).
And this new instance also got some error code opening machine-id file 
and rewrote it. And exited later for some reason.

What measures does DBus take to prevent such things?
Or what would be an explanation of the observed behavior?

Yuri