heres a few steps to fix this.
1> download quickpar from here: quickpar downlaod page
install it
then download this file to your desktop: par2 file - yousendit
open this file with quickpar. it will scan the files and report any broken files.
tell me how many blocks it needs to repair. if the "repair" or "rename" button is selectable then just click it and it will repair the damaged file. then after it has finished the repair you can go back and extract the files
if it says it needs more blocks then tell me how many and i can send you the file to repair it