Answers:
A few things could end in this (assuming Norton's bloatware isn't freshly flaking out) approaching you are connecting to a different wireless web, or through another computer via Internet Connection Sharing (ICS) and the gateway tool on the LAN have changed, someone is blatantly spoofing the MAC, or the ICS gateway have undergone a NIC upgrade / progress.
If you are running wifi lacking turning on the WEP/ WPA/ WPA2, and shifting the evasion login for the access point you are asking for trouble. it is best to restrict router access to a small catalogue of internal IP's (ie 192.168.1.2-192.168.1.5) and disallow remote admin . Or if your router/ gateway supports it map static ip address for respectively set MAC, solitary allowing router access from one specific internal IP, and disabling DHCP requests and the SSID broadcast entirely.
If I received a message or notice the gateway MAC have changed, I would no problem look into it rapidly. It is also possible , if you enjoy two or more machines in the LAN that are DHCP enabled, that impossible to tell apart IP address have be assigned to different computers.Thus Norton is trying to sort why its reading two different MAC address for 192.168.1.1
Depending upon your smooth of network experience, you may want to run a packet takeover surrounded by promiscuous mode to analyze the traffic, collision rate, etc.
If you can't acquire it sorted, download Wireshark & WinPcap;
http://www.wireshark.org/
Run a occupation for a bit surrounded by PROMISCUOUS mode, and email me the log, and I'll look it over for you.
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