Why do I blame the modem? Because power-cycling the modem resolves the issue. I can't understand why that should be the case, but the evidence appears clear.
Some history: For several years I have powered down the modem overnight. Recently, thinking that I might be stressing its electronics, I stopped doing the power down.
Hmmm ... sorry no example. Even tho its in a code block, the message error checker would not let me post.
Your solution is correct although the diagnosis is not. Your modem's not near death but your wifi may be getting stressed with repeated weak hits to where the local DNS cache is getting trashed. Rebooting the modem clears the DNS cache and solves the problem.
@Geoffrey Leach wrote:
Wi-Fi is not involved. The modem in question if the Hughes satelite interface modem.
It can happen regardless of the method of connection (WiFi or LAN).
True. Have mostly seen that happen when there's a storm and the signal quality is very low.