there is an alternative way to transfer items (but not zeny) between accounts. Go to an empty building somewhere (I won't say where it is that I do this) on both characters. Drop the items on the giver, pick them up on the givee. As long as you don't have a massive internet failure you should be able to transfer the items fairly smoothly.
do note rhino is NOT talking about dual-clienting. she is merely saying both characters should be in the same location that you wish to transfer to. you would be logged on one account, drop the items, then after logging out of that account, log in to the other and pick them up.