findlib 1.2.1 compatible with Ocaml 3.10.2 ?

Dear all,  

I have just met a wired exception when trying to compile my ocaml code:
Uncaught exception: Invalid_argument("waitpid not implemented")

Platform: cygwin, ocaml 3.10.2,  ocamlfind 1.2.1
loading unix and postgresql package

As far as I can see it's a problem related to the Unix module. (But it's working fine before I moved to ocaml 3.10.2) I did the following tests:

(1)  ocamlmktop -o mytop unix.cma

$ ./mytop
        Objective Caml version 3.10.2

# Unix.time();;
- : float = 1206712146.

working fine

(2) ocamlfind ocamlmktop -o mytop2 -package unix -linkpkg

immediate exception:
Uncaught exception: Invalid_argument("waitpid not implemented")

Surprisingly, you can find 'mytop2' created!!! and working

$ ./mytop2
        Objective Caml version 3.10.2

# Unix.time ();;
- : float = 1206712304.

Is there any one know or has met this problem? It's a problem related to cygwin, findlib, or the ocaml 3.10.2?

Thanks for any help!

Conglun