Another fairly well documented issue by now. Our friends at weather.com made some network changes that break the code that fetches weather maps. The basic problem is that w3.weather.com no longer works, so instead you must now use www.weather.com. The wiki has a writeup on fixing this: http://knoppmythwiki.homelinux.org/index.php?page=MythWeatherFix

BTW - not mentioned there directly is how to re-enable animated weather maps. It seems that the setting WeatherWantAnimated and the ability to enable it from the setup menus got lost between 0.16 and 0.17 due to a code regression. However the working bits are still in place. All you need to do to reenable them is poke the value in with a bit of SQL: