Serialize a custom class on IOS

Hi,

I'm trying to serialize a class, it works very well on my Mac but crash on IOS.

I was under unity 4.1 pro trial before, and it was worked too on IOS. But it's doesn't work anymore since I'm under Unity basic 4.2 version

Here is my code :

 var b = new BinaryFormatter();
 var f = File.Create(Application.persistentDataPath + "/"+fileName);
 b.Serialize(f, infosInstance);
 f.Close();
 

InfoInstance is a custom class with only string variables...

If I try to serialize only a string, it works but crash with a class.

Any Idea, I've read on some threads it's could be because I'm under basic Licence. Is it ?

Thansk a lot.