Too much lube in your die, I think. Either use less lube per case or take out the die every 4-5 cycles and clean it out. That's been my experience at least with some larger cases.
Take your die apart and clean it with a degreaser. Also your die will have an air escape hole/ pressure relief hole some where close to the shoulder of the case. Make sure it is not clogged. Third, when you tighten down the lock ring try not to cover the little hole with the lock ring.
Make sure not to get ANY lube on the necks or they will dent, use just enough for a smooth resize, I just give mine a light roll over my pad, making sure none gets on the necks, that's all.
I agree with most of the reply's. Clean the dies and chek that the vent is clear and I particuliarly agree with meichele, There is nothing better than imperial sizing wax 1 little can goes a very long way. I size two and skip lubing the thrid and start this sequence over on everything except when forming a new case to some other than it is.
RH