More information. I enabled log level=DEBUG and I see a continuous stream of these messages:
NetworkManager[8461]: <debug> [1361823070.525214] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 2 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.525492] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 2 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.525782] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 3 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.526063] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 3 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.526410] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 3 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.526692] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 5 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.526972] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 2 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.527251] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 2 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.527582] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 2 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.527862] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 3 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.528142] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 3 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.528422] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 3 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.528700] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 5 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.528990] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 2 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.529266] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 2 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.529547] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 2 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.529826] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 3 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.530105] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 3 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.530419] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 3 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.530700] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 5 flags 0x11043 NetworkManager[8461]: <debug> [1361823070.530979] [nm-netlink-monitor.c:167] link_msg_handler(): netlink link message: iface idx 2 flags 0x11043 -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to network-manager in Ubuntu. https://bugs.launchpad.net/bugs/1111926 Title: NetworkManager increases CPU utilization Status in NetworkManager: Confirmed Status in “network-manager” package in Ubuntu: Confirmed Bug description: Observed in systems if gnome gui is installed. NetworkManager will usually one of the cores to 100%. Killing unused services like avahi and cups didn't seem to help. Restarting the dbus service fixes the issue /etc/init.d/dbus restart Need to find root cause. To manage notifications about this bug go to: https://bugs.launchpad.net/network-manager/+bug/1111926/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp

