Take a look at your weather underground settings.
under Update every 1 minute, 10, etc.
if I do that, it will update
12:01, 12:10, 1:01, 1:10, 2:01, 2:10 etc, but not multiples.
you can see this in effect at:http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=KAZTUCSO57&day=10&year=2012&month=4
take a look at hours 2-6, thats some data I was trying to fill in after my internet IP address hung.