[Plank3]

When I request a GRIB from within GPSNavX, the email I get in response is this:

Grib extraction failed (zero-length file, data files could not be downloaded)
request code: grib:33N,33N,118W,117W|1,1|0,12,24,36,48,60,72|WIND,PRMSL

Why am I getting this error?

Thanks.

[GPSNavX]

Because the chart you are using covers too small of an area (a large scale chart). GRIB data is on increments of one degree - ~60nm points. Try using a small scale chart when you "Request GRIB" that covers a larger area and then you will not get that error.