Function causing Loop

[Cyhawk]

Hello all, i have a small question.. I found a bug in a OBJ_DATA function i 
wrote for my item generator. It seems, whenever this function is called,
it causes a loop. (sometimes later though.. its very odd, inside the shop 
generator, the mud loops on startup, but no errors, when i use a function
that calls on it, it works.. but anytime i try to save_char it loops, 
copyover/save/quit) and im wondering.. What logic error am i missing?
(while writing this.. i thought about something and re-wrote the function 
and it ended up working flawlessly.. though still... what mistake did
i do here?)
The function is below

As always, help is much appreciated =)
-Thri

OBJ_DATA * weapon_plus_five (OBJ_DATA * obj)
{
        AFFECT_DATA *af = new_affect ();
        char prefix_full[MSL];


        sprintf (prefix_full, "(+5) %s", obj->short_descr);
        obj->short_descr = str_dup (prefix_full);

        af->location = APPLY_HITROLL;
        af->modifier = 5;
        af->where = TO_OBJECT;
        af->type = 10;
        af->duration = -1;
        af->bitvector = 0;
        af->level = 1;
        af->next = obj->affected;
        obj->affected = af;

        af->location = APPLY_HITROLL;
        af->next = obj->affected;
        obj->affected = af;

        obj->cost += 15000;
        return (obj);
}