I just ended up here by chance when searching the web for more information on what happened today, which also affected one of my applications. Anyway, the simple solution is to omit the '&prod=xoap' part from the URL. Previously the URL I used to access the XML data feed (as per their SDK) was:
"/weather/local/" & LocationCode & "?cc&dayf=5&unit=" & IIf(Imperial, "s", "m") & "&prod=xoap&par=<partnerID>&key=<LicenseKey>"
replacing this by
"/weather/local/" & LocationCode & "?cc&dayf=5&unit=" & IIf(Imperial, "s", "m") & "&par=<partnerID>&key=<LicenseKey>"
gets the feed back. I'm extremelly PISSED OFF with Weather.com. I called them today and they were unable to give me any info or state this simple solution, rather implying (on the phone and on their email sent barely 6 days ago!) that my application was not following their TOS (which is impossible to verify as they provide no mechanism to do so). They promised to call me back but never did.
Now I have to make a new emergency release of my application (with half finished new features I've been working on!!!!) to fix a problem they caused in the first place.
You can read more about this in the Winstep Forums.