bus error when use threads and native mode on Mac

Hi,

I am trying to use threads in my lablgtk application but it crashes (I am on Mac OS)
in native mode with a mysterious "Bus Error".
I have linked my program with -thread and use 
  GtkThread.main ();
in the main but it does not work. It works nice in bytecode mode though.

My program displays some fancy graphics with cairo and then run in the background using a thread
some heavy computation that I access on demand from the main thread when the user click
on certain things. 

My code also uses GMain.Idle and Gmain.Timeout (don't know if it's relevant).