Unity 4.5.4. Development Build Flag not set cause freezes and longer game object init time

Hi,

I was investigating about a freeze that happens when I activate a group of game objects. (roughly 50 /80 objects) on iOS.
That freeze happens only once during the lifetime of the application once started. As an example: I loaded a scene, I activated the game object group parent. The game block for 3 seconds or so. Then I changed the scene, loaded the previous one again and redo the test. No freeze at all.

I notice that when the Development Build is set the game work as expected, just a little spike. But when I start using a "release" like build (no development build, no script debugging, fast call etc) the game start freezing.

I tried different combinations (development + slow call, no dev + slow call, etc etc) but in the end what make the difference is the Development Build flag.

What it really does under the hood ?
Is there anything I can do ?

What I'm going to do now is to profile manually using some timer various pieces of code to discern at least who / where is the time spent. But because It is only once I suspect it is something unity cache (but really don't know what)