corrupted .rar file / incorrect password (help please)

hi there,

i have been sent several .rar video files and usually have no problem expanding them. i generally use Rar Expander and UnrarX. this time however, half-way through the expansion, it always stops, saying the password is incorrect or the file is corrupted. whilst it is being expanded i can watch the file up until the half-way point by locating it in finder. my mate has constantly tried uploading and sending me the file that seems to be corrupted but it's always the same issue. is there a way i can start the expansion after the corrupted file so i can see the other half of the file or expand each file individually. i also have VLC Rar Loader but for some reason I can't open this individual files in this either. please help, i would greatly appreciate.

thanks in advance, ravi.