Powered Rails no longer accerate moving cards

Pre 1.5.1 simple tracks of 64 + 8 powered rails would keep transporting an occupied mine cart. Even though the rail IS powered.

What I expect to happen:
Push the cart, jump in, hit the powered rail and accerlate to top speet.

What actually happens is:
The cart does not accerate and peters out.

Cross Section

-----========---------
xxxxxxxxxxxxxxxxxxxxxxx
xxxxxxRxxxxxxxxxxxxxxxx
— rail
==== Powered rail
x any static block (dirt, cobble, stone)
R is redstone torch powering block above it

Steps to reproduce:
1) build above
2) push cart toward activated powered rails
3) jump in.
4) Let Tails close this too becuse its a duplicate of 12575. (sheez, is there no qa on basic features ? )