Via Jim Wexell, news that Ben has been experiencing headaches this week and won't play. I haven't found any other confirmation, so take this with a grain of salt for now.
UPDATE: John Clayton confirms, Dixon will start, Palko will be signed and Shaun MacDonald released.
UPDATE 2: Palko signing confirmed on steelers.com.
UPDATE 3: Confirmed on steelers.com, Dixon will start, Ben will be the no. 3 QB.