For whatever reason the Wifi on my brand new iMac will not stay connected, and the only way to reconnect is to turn off the airport and turn it back on. The airport will say it's connected, but I can't ping anything or access the router's admin page. I was able to reproduce this with three different routers. It seems to disconnect when the display goes to sleep and does not reconnect. I don't have this problem with any other wireless device on my network. Ideas?