Jal5, I would bet the farm that your seating die is turned into the press too far. I made this mistake in the past with a 270 and needed a ramrod to get the case out.
Re-set your FLSD back a hair and make sure the sizing grease/spray doesn't get on the shoulder.
It isn't your FLSD. They are made to be "camed over" when set against the shell holder inorder to set the shoulder back a bit.
The seating die, on the other hand, will crush the case if it is set too close to the shell holder. It is trying to apply an exsesive taper crimp to the case and pushing the neck back into the case shoulder.
place a sized, primed, and charged case in the press; raise the ram to top stroke; screw the seating die into the press untill it hits the case and stops; lower the ram and case; unscrew the seating die 1-2 turns; place a bullet in the case and raise it agian to top stroke lower it, check seating depth and adjust seating stem. Repeat untill desired OAL is achieved.
This is your problem. Nothing else.