For most of its GRIB files PocketGrib uses the public GRIB weather service which is provided for free by the Saildocs organisation. They seem to be having a problem with their online GRIB servicee which is causing the error.
An alternative way to get GRIB files is to use one of the GRIB email services below. The links will open a request email in which you just need to set the latitude/longitudes to your desired area.
This email address is being protected from spambots. You need JavaScript enabled to view it. - this sample will download wind and pressure
This email address is being protected from spambots. You need JavaScript enabled to view it. - their email service is actually working but very slowly due to their current problems
Also, here are a couple of GRIB files that cover Europe and North/Central America
