Powered rails don't power a minecart

In a creative world created in 1.5 and recently upgraded to 1.6.4, I put down several blocks of powered rail powered by a redstone torch. The minecart doesn't accelerate over the powered rail The rail glows, but it acts as if it's not powered. It doesn't act like a brake either, it acts just like normal rail But powered rail that I put down in 1.5 still works correctly.