I have a user who's on a brand new Lion iMac and is having constant network issues. I know there have been a lot of issues with the Wi-Fi in Lion, and this seems to have the same symptoms with Ethernet. I've eliminated any physical problems with cables/jacks. Sometimes renewing the DHCP lease will fix it, and sometimes it needs to be rebooted a couple times before it works. Almost every morning she said she has to reboot as many as 3 times to get it to connect, then at random points throughout the day it drops the connection. Any ideas? Edit: It turns out it's a 2011 model.