...some kind of network failure. This morning, I saw a new icon in system tray at the bottom of the screen: "Diagnostic and Usage Messages". I opened it to find a lot of unfamiliar, disconcerting messages since 23 December. As I recall, my kid complained that he had no internet signal, and sure enough, he didn't. But he did not say why and I did not ask. I shut down the machine and rebooted and somehow, for some reason, the signal came back. I went about my business and didn't give it a second thought. Here's a message line from the "Diagnostic and Usage Messages" box. 12/23/14 6:32:51.420 PM airportd: SCPreferences(com.apple.framework.CoreWLAN:com.apple.airport.preferences.plist) lock delayed for 6.549 seconds com.apple.message.domain: com.apple.SystemConfiguration.SCPreferencesLock com.apple.message.signature: com.apple.framework.CoreWLAN com.apple.message.signature2: com.apple.airport.preferences.plist com.apple.message.value: 6.549 SenderMachUUID: 880D9443-CCBA-3856-BBBB-00D6D1360F8F Here's the most recent message: 12/31/14 10:36:18.570 AM loginwindow: com.apple.message.domain: com.apple.BezelServices.IdleTimer com.apple.message.result: pass SenderMachUUID: C6C1FCD6-5FBA-3B2D-9322-367F697EDAAA ****** Should I be concerned? If so, what might be causing the messages, and what to do? I am running OS X Yosemite v 10.10 if that matters.