I have a support ticket into Weather Underground on this same issue, but no response yet.
I agree with previous posts that Wunderground is a really good service, and I rely on it very heavily. The sporadic data losses over the past few weeks has been pretty frustrating though. We're right at the start of the monsoon season in Arizona, and I hate missing the first good Tstorms of the year! Hope they get it fixed.
(KAZSEDON3 Casa Manana, Sedona, AZ)