before you click on the item in your inventory... hold down the Control button... then click on the item and drag it to where you want it to be (in this case the floor, so that your other char can pick it up.
There will now be a little window open asking you how many you want to move.
You can also move them between the 2 char's inventories, if you open 1 inventory, then move the window and then click in the other char and click in the inventory button (pressing i wont work).
