Sorry for bumping such an old thread, but when googling this error:

Error in Installation File (ubi.ini)

This thread in the only result.

After not being able to find any help on the net, I managed to fix the problem myself, all I had to do was copy the:
%windir%\Ubisoft
Folder to the game installation folder (default is c:\ubisoft\raykit).

I hope it will help other people with the same problem.

P.S. There is a "patch" (It's actually just an installer+DOSBox) for Rayman Gold (aka Rayman Designer or Rayman World) by Opaquit (pok2) which also solves this problem. I found out about it only after I fixed this error by copying the directory mentioned above.