phantom procedure - mi_prepare() fails sometimes, but sometimes do not

Had anyone problems with mi_prepare() and stored procedures? Env: IDS9.21.UC2 Linux Redhat 7 - kernel 2.2.16 The following code is behaving strangely, the prepare call fails sometimes, sometimes it don't. Nobody modifies the procedure, that's clear. Any ideas ? #include <mi.h> int main() { MI_CONNECTION *conn; conn = mi_open("master",NULL,NULL); if(conn != NULL) { if(NULL == mi_prepare(conn, "execute procedure webuser_mgr(?,?,?,?,?,?,?,?)", NULL)) fprintf(stderr,"Prepare failed!\\n"); else fprintf(stderr,"Prepare ok!\\n"); } else fprintf(stderr,"Connection is null!\\n"); return 0; }