Device must be rooted
Root Explorer installed
Fixing the problem:
Using root explorer navigate to System/etc/permissions
Open platform.xml using root explorer's Text Editor
Find the permission "Write_External_Storage" and there will be the permission group: "sdcard_rw"
Add another group directly under that one: <group gid="media_rw" />
Save changes made in the file and exit
Reboot your device
Done! Now apps have the permission to write data on the external sd card.