Vista - "Parameter is incorrect" for SOME file copy SharePoint to Vista NO

I am trying to bulk copy (copying a lot of files) from an Explorer window
mapped to a SharePoint folder. Some files fail to copy with a "The parameter
is incorrect" error. The problem is unique to Vista systems - it doesn't
occur with any non-Vista systems I have tried (with the SAME files), and the
problem occurs with every one of a variety of Vista systems of all versions
at a lot of locations, so I'm pretty sure the problem isn't related to
firewalls or system configurations. Most files copy fine. A few files of a
large group fail to copy with the "Parameter is incorrect" error. In some
cases, files that fail one time work the next time, although some files that
fail do so repeatedly. For those files that fail repeatedly, they fail
whether I try to copy just that one file or the file is part of a bulk copy
set of files.