This will be lengthy but thorough. Background: I've been having intermittent internet drops for the last 4 months, seemed to start with the installation of a modem I bought so I could save the $5/month charge to use an ISP-supplied modem. The router I'd prefer to use is a Netgear WNDR-3700, my "backup" and the one that I've been using for a week to test a theory is a Linksys WRT54G-L with DD-WRT on it. Yesterday, all seemed well when I got home from work, everything seemed to work fine. I went out for a bit, came back and all went down the tubes. I had poor connectivity, if at all. No changes were made yesterday, except when I started troubleshooting. I swapped to the Netgear thinking maybe I was getting interference on the 2.4 Ghz band, while I could use 5 Ghz on the Netgear (I can pick up almost a dozen other wireless networks when I scan). I first noticed the issue while trying to upload a photo using iPhoto. I try connecting directly to the modem, minimal change, so I call my ISP, spend an hour on the phone with them and get nowhere. While doing this, I start seeing a pattern, when my Mac is plugged into the modem directly, I still have issues. When I plug in my self-built Windows desktop everything is perfectly fine. I shut EVERY device off (iPad, Android tablet, HP printer, desktop), unplug the modem and the router (the Linksys at this point), plug in the modem and then once that booted the router. Once the router was up I booted my desktop, all was good (start running speed tests at speedtest.net after each device). Turned the printer on, fine. Android tablet, fine. iPad, fine. Booted the Mac, down the tubes instantly. When I log in to the Mac, Chrome comes up automatically (haven't figured this out either, I've removed it from login items), none of my tabs that load automatically can connect. I have CrashPlan for backup, that can't connect, Google Drive can't connect. I start killing the extraneous processes that use network (Drive, CP) and still can't connect and see high outbound network usage. At this point it's 11:30 at night, I close the lid on the Mac and go to bed. I woke up this morning and it was like there was never a problem. I have no idea what's going on, the Windows convert in me wants to just wipe it and start over but there HAS to be a better way. I used nettop in terminal but didn't see anything overly disturbing. Thanks for reading, hoping someone here has ideas. Update, after thinking about it, I installed 2 updates to the Mac yesterday, one was for RAW compatibility, the other was a security update. I wonder if the security update caused this.