This is a known problem that occurs only between Netware 5.1 and Win 7; there are other posts in this Forum about it.
AFAIK, these “Copy problems” happen only with IR4 version of Client2.

You can workaround it now by using Client2 IR 3 instead of IR 4; pay attention to the fact that you could then experience other problems, in particular when you write/update files on server, so check the integrity of data on server after writing. I can suggest (from my personal experience) to turn off File caching and turn on File commit in Client settings.
The good news is that Novell is currently working on this issue, and it could be solved by Client2 IR5.

Update:   Was Fixed in IR5