error in reading an arc grid file

Hello

I am using the mapping toolbox (last version under matlab 2013a) on a linux laptop (kubuntu 13.04). I get an error when I try to read a file

alt=arcgridread('ARG_alt.grd'); Error using arcgridread>readHeader (line 82) Unexpected tag '[general]' in file header (line 1).

Error in arcgridread (line 36) hdr = readHeader(fid, isURL);

I downloaded the data (= altitude in Argentina) on the Diva website http://www.diva-gis.org/gdata. I add that I am a newcomer in the mapping toolbox.

Thank you in advance

Vincent