Just this new iMac doesn't have internet connection?

My network is working fine on two other macs running Mavericks. I purchased and set up a new iMac this week and it had been running fine. But this morning my hope network reads as though there in no internet connection...the wifi is fine and strong. Also, airport utility can't see my express or extreme.

Oddly though, the iMac and connect to my neighbours open network just fine.

I've tried starting and restarting, even checking to see f the problem was duplicated on the guest account...

Any ideas?