I found it.
In fact everything was because of this line:
undefined symbol: _ZN10MNTManager10DisplayAllEv (/apollo/Developpement/Build-GCC4/Obj/Linux-PORT/i586-GCC4/lib/libtestGuiMnt.1)
There is an undefined symbol of MY library. I defined it and problem solved!
Please see my original post: segfault using SWIG converted code for tcl
The confusion was, my program crashed in the middle of tcl wrapper functions (where my undefined symbol was not involved at all). I don't really know why but that's it..
Hope it will help others!