problems copying files

Hi - i have just developed a problem coping files from one external hard drive to another.
all the folders and su folders copy across ok - but they are empty with no files in them?
any help would be appreciated
I apologise if i have posted in the wrong place
Anthony

Note: I moved this thread from our 'off topic' forum, since we do actually have a forum specific to discussion about 'OS X Operating System' functions.