The blocks were working fine for me, unless they're supposed to be stronger.
As the second speed-up block only returns you back to normal speed after the slow-block is used, it isnt enough for you to make the final jump. I came up with 5 - 6 different ways of getting to the last jump but was only ever left with one jump block and one speed-up. But, as I said, since I was already slowed down, it just returned me to normal speed.
If thats what you mean by not working, then yeah thats it :)