Just throwing this out there, if you reference this picture of the overhead panel.
Photos: De Havilland Canada DHC-8-402Q Dash 8 Aircraft Pictures | Airliners.net
There is a switch on the Ice Protection sub panel that says "REF SPEEDS" I'm curious as to how much this would alter the speeds in this setting's and hypothetically left in the normal or off position could this have been a factor in this accident.
I'm sure the good people down at the NTSB will be looking into this eventually but are there any Q400 Drivers on here that could shed some light?