issue with MySQL Query Browser

Hi,

I've created several stored procedures and functions this week end and
everything works great under command line window (results are what i expect
to).
however, stored procedures do no work under MySQL Query Browser.

here is what i use to do :

call my_stored_procedure(IN arg1, IN arg2, OUT @a, OUT @b);
select @a;
select @b;

this works under command line window but not under this GUI tool, why ?
is there something particular to do for that ?

thanks a lot for help.

Alain