I have never made partitions on an sd card. I just format them in some old microsoft format and they work.
Assuming the problem is on the sd side and not the source side, and the above idea doesn't help, this procedure checks for permissions and changes them if necessary. (No guarantees this is correct. Use at your own risk.)
Using Ubuntu 12.04
I just stuck in my sd card reader into my computer with an sd card in it.
I opened up nautilus clicked to expose the full path of the sd card, exposing it as /media
I opened up a terminal window and changed to /media
then ls -la to see what is there and what the permissions are
drwx------ 12 xxx xxx 32768 Dec 31 1969 1116-06EC
I think the drwx means that I can write to it.
(Also, I listed 1116-06EC to make sure it IS the sd card. You card will most likely be something different than 1116-06EC)
But if "drwx ..." is not the case, I would do something like this
chmod -R 777 /media/1116-06EC
and if that doesn't work
sudo chmod -R 777 /media/1116-06EC
That will make it so anyone can do anything to anything on the sd card. (You could do it without the -R so it doesn't change permissions on everything on the disk. )
Actually I would just start off with the sudo form but some people are sudo careful.