A computer or device on the network restarted during the mapping process. To fix this problem, wait for the computer or device to finish starting, and then refresh the network map by pressing F5.
Your computer is connected to a wireless network and the wireless signal quality is poor or intermittent. To fix this problem, move your computer closer to the wireless router or access point.
A device on the network, such as a hub or switch, is not working properly or is not compatible with the Link Layer Topology Discovery (LLTD) protocol, which Windows uses to create the map. To fix this problem, disable the device, turn it off, or remove it from your network.
Responses from other devices on the network are delayed or there is an incompatible router on the network. If responses are delayed, try waiting a few minutes and then refreshing the network map by pressing F5. If a router is incompatible, try disabling the router, turning it off, or removing it from your network.