Steve is right...Wunderground DOES have some automated QC stuff in place, so if you are running without the proper Radiation Shield on your temp sensor and are spitting out BAD data for your area compared to surrounding stations, they could theoretically KICK YOU off the site, albeit a very rare thing to have happen. You will continue to see your data on your actual PWS page, but the section on the right will have Nh in the data fields instead of data. Also, your little map circle thingy with your temp on it will be missing on the map. If that is happening, then your station has been removed for data accuracy issues.
Far more likely is just issues with Wunderground. They have them daily with one part of the site or another. I have learned to just ignore them until I see a problem lasting longer than 24 hours, then I email them. It can take up to 3 days to hear back from them, IF they reply at all. I suspect that they are very short staffed, and often have people manning the support section that know absolutely NOTHING about this stuff. I can tell from the relevance of the replies I often get back, that I am dealing with a TEMP worker or a Secretary who is filling in.
Not good, but that is the way it is over there right now.