I can't understand what's wrong. My fstab looks like this:
UUID=843671A53671993E /mnt/toshiba ntfs defaults,uid=1000,gid=1000,dmask=027,fmask=137 0 0
/mnt/toshiba (and sub-folders) permissions are:
Access: (0750/drwxr-x---) Uid: ( 1000/ pi) Gid: ( 1000/ pi)
Event with all these set, when trying to write on /mnt/toshiba with the user with gid=1000, I get "Permission denied". The filesystem is NTFS.