Does two pairs of socks feel tight? If your feet are too tight in the boot, blood has a hard time flowing and warm blood is what heats your extremities.
Stupid comment but did you maybe wash you boot liners in preparation for your trip? I went ice fishing with the brother-in-law and a few others (Hightower, are you out there?) and one of them had washed his felt boot liners the night before. He thought two cycles in the dryer would be enough to dry them, guess what, two hours later and he had frost bitten toes. We almost had to cut the boots off because it hurt him too much to pull them off.