How to crop profile picture of facebook in Round shape?

I am using Unity4.5.1f3 and Unity Facebook SDk 5.1 in my game.

All I want for now is to download and use facebook user profile PICTURE(But in Round Shape,Normally, I hate square(s))....

So far, I am able to download profile picture and use it as sprite in my scene...

And to make it in ROUND shape I found this..http://answers.unity3d.com/questions/650732/cut-texture2d-in-circle-format.html...which is correct to my knowledge...

when i run this code unity gives me an Exception : "UnityException: Texture '' is not readable, the texture memory can not be accessed from scripts. You can make the texture readable in the Texture Import Settings."

If it were and usual texture which was stored in hard drive i could understand that i need to turn it into advance type in INPECTOR..But how could I Solve this issue...??

Any hint/suggetion will be very gratefull....

Also tell if I am doing whole things in an inproper way...

 

You can use a masking shader.

http://wiki.unity3d.com/index.php?title=Texture_Mask

To make textures readable, set them to advanced in import settings and check the read write box.