Experts and BHG readers answer.
Your mystery vine sounds like Echinocystis lobata, commonly called wild cucumber, wild mock cucumber, or balsam-apple. It has a palmate leaf (hand-like in its veination pattern) with pointed lobes. It flowers from June through October with delicate-looking, six-petaled white blooms. Wild cucumber produces fat, oblong spiney pods. It is considered a weed, and has become invasive in some areas of the United States.