Adultery: voluntary sexual intercourse between a married man and someone other than his wife or between a married woman and someone other than her husband; also : an act of adultery.
Seems straight forward and certainly not commiting adultery would assure harmony in the home but the key is not the sexual aspect but the unfaithfulness to ones vows.
But this has come to mean, at least to Jews, Christians and Muslims any sexual contact between anyone outside of the safe confines of marriage. Even when both parties are unattached.
Sin therefore can be explained to mean just about anything one wishes it to mean. In the original sense of sin as being a physical force we have the parallel in the actual beings that were unleased from the box. Much as sin that crouches at the door in the biblical account. As to disobedience, Pandora did not own the box, it wasnt hers, she was holding it in trust with a single prohibition... Do not open it!
One part of the story that I think is often neglected is that before she opened the box she spent all her days looking at it, running her fingers across it and basically coveting it. Mention is made that her husband was away for only a moment when she opened it. This to me indicates that she was being a bit sneaky in her actions and waited for a moment to see what was inside. This was an act of disobedience, especially when one realizes that the stranger who left the box with her was in fact Zeus.
Again another similarity to the biblical account. God/Zeus put the temptation of the fruit/box in the garden/fig tree and eve/pandora was tempted by whispers from the box/serpent and she unleashed knowledge of evil/evil beings from the box but was also granted the opnly thing that could save the world from what she wrought, hope/life giving. The only real difference is that the bible story has become corrupted over time and turned into a method to hate women and hold them in lower standing but I dont think this was the original intent of the story at all.