It works for me. Make sure your not in a golden age tho. It doesn't work during a golden age
Another thing you could do is try redownloading the trainer.
[Edited by Chunder, 10/2/2010 5:53:56 PM]
I'm getting the same problem. It looks like this might be an issue with Civ 5 itself rather than the trainer - there's a thread on the Steam forums about this issue:
Use the building reduction command for wonders. Just open city menu, activate the command, select the wonder, and then enter/exit the city (click, esc, click, esc) and active the building reduction command when it deactivates. Until you get the building down to one turn to build. (Some wonders wont work tho, like the Utopia project, Manhattan project, etc)