Movie complete implodes in last half hour

I actually thought the build up was decent and the actors weren't half bad (for a budget horror flick), but then this thing went completely off the rails at the end. It wasn't scary, it was just "hey, people go nuts in blizzards in this pass and kill each other." Flop. Without the Donner party reference, it wouldn't have the least bit of supernatural tension.

Sad thing was, about 45 minutes in I was thinking, hey, this isn't half bad, wonder why it got rated so poorly... and then the end happened, and it was all clear to me.