Thanks guys. A few follow-up questions:
1) I assume you're saying the lump got damp while being stored in the basement, yes? Also, the humidity at burn-time had little to do with it.
2) Where/how do you store your lump? I don't have many options other than to store them in the basement.
3) Are my current bags of lump redeemable? I.e. if I store them in a dryer place will they eventually dry out?