Quote:
There have been a number of issues that Vista users have reported relating to copying and moving data, especially large numbers of files. Often there can be multiple errors at play making it difficult for Vista users to track down the problem, in fact very often there is little indication that file copy operations haven’t completed correctly. It’s only when the user checks the number of files in source and destination that they realize they have a problem.
read the link for more details.
one bit of semi good news. there is a fix slated for SP1 and a hotfix that you must request that is available today.