I have an old Vita-Mix model #517 that was working OK until I cleaned the container. I filled it with hot water and baking soda, and let it soak to remove some residue in the bottom, and now - while the motor runs fine - the blades won't turn. I wanted to give this as a gift, but obviously don't wish to give someone something that isn't in good working order. Any suggestions on getting this thing working again will be appreciated. I need to get it going or will have to find something else for the gift.