If you're not careful when you open the pack, you will destroy the cells. You just pull it a little and let the tape release. If you bullied it apart, I bet it would spark.
It shorts the pack internally as you rupture the inner structure.
I've had them act like that before (lose a cell)...the fuse links are blown on the board. In my case, it's always been because I hooked up the battery backwards (who...me???
). I've heard of them being bad like that out of the box...they'll replace those.
I wish you lived around here Porkey...you seem like a cool guy.
A bit clumsy and notsogood at spelling...but you do sound like a fun guy to hang around with.