I've found this in /var/log/messages:
nm-dispatcher.action: _nm_object_get_property: Error getting 'Options' for /org/freedesktop/NetworkManager/DHCP4Config/2: (9) Interface "org.freedesktop.DBus.Properties" isn't exported (or may not exist), can't access property "Options"
It seems harmless though since my network works properly.
This issue has been proposed when we are only considering blocker
issues in the current Red Hat Enterprise Linux release. It has
been denied for the current Red Hat Enterprise Linux release.
** If you would still like this issue considered for the current
release, ask your support representative to file as a blocker on
your behalf. Otherwise ask that it be considered for the next
Red Hat Enterprise Linux release. **
*** Bug 620725 has been marked as a duplicate of this bug. ***
warning is mostly harmless unless a dispatcher script wants to grab the DHCP options out of the environment, which (at this time) few do.
Red Hat Enterprise Linux 6.0 is now available and should resolve
the problem described in this bug report. This report is therefore being closed
with a resolution of CURRENTRELEASE. You may reopen this bug report if the
solution does not work for you.