Li-Po's are dangerous, but so are Ni-Mh, we've all just become comlacent with the familiar cells.
There's a good chance at least one of the cells is damaged, but they're not cheap so it's worth trying a salvage them if you can. As said, if they're puffed, don't even risk it. If they're not puffed, it's worth a go- using reasonable and proper safety precautions. When Li-Po are damaged their cell chemistry can lead to small explosions and self fueling fires which will burn for a couple of mins even if deprived of oxygen. That's why charge pouches are necessary- to contain the fire until it's finished.
Take care and things will be ok whichever way it goes.
Li-Po cells have the cell materials in a aluminium satchel, as opposed to a steel can that we're used to. These pouches are vacuum sealed to keep the cell materials pressed against each other. When cells are abused, either by drawing too much current from them (that's where 'C' ratings come in) overcharging them, overdischarging them, or any other abuse, sometimes gas can be given off. This gas is retained in the pouch, but then the pouch is no longer in vacuum, it's pressured by the gas, causing it to 'puff'. Once the cells are puffed the internalplates have much more freedom to move around (they are sealed in by vacuum remember) and this makes inter short circuits much more likely, and a serious internal short is what leads to the fire.
So because of the concequences it's a MUST that after any cells have had abuse, you monitor them closely during charging/use, and also keep an eye on them in storage, and store them somewhere safe, life in a li-po sack in a steel box with a secured lid but with a breath hole, on a concreate slab or other heat resitant area.
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