Make sure you have the latest version installed (2.03).
I recently made a couple changes in NOAA winds to correct
the problem of WR'ing in the 2 hours before the update.
(Go to http://www.tecepe.com.br/nav/vrtool/download.htm
and update using vrtool.zip
The problem you report seems to be related to missing wind forecasts.
Make sure the forecasts are loaded for all times (0, 12, 24 etc)
I noticed that sometimes the NOAA downloads fail for a specific forecast,
for unknown reasons. All winds are 0 for this particular time.
In this case, repeat the wind download.