Network Files and Folders disappear using Vista

Hello.

I have an issue with a Vista Business user losing files and folders on a
Windows 2003 SBS network.

In the first instance, quite a few files disappeared from the user's My
Documents folder which is redirected to the SBS server.

About a month later, another instance arose. He was organizing folders on a
network share. He was moving folders, which each contain a few files, from
one folder to another. He moved a folder, opened that folder to verify the
contents, then went to go back to the original folder. At this point he found
that the original folder was gone. I search the entire directory on the
server, and it was indeed gone.

I restored that folder from a backup. He then proceeded to work more with
these folders.

He right clicked on one folder and chose to delete. The message appeared
that stated that the [folder name] folder would be deleted, are you sure? He
clicked yes. Then, the message came up that stated that over 300 files were
being deleted. Not only was the folder deleted that he chose, but the entire
parent folder was also deleted. I again had to restore from a backup. I again
search the folder structure and they did not get moved to another location
inadvertently.

I have applied the registry fix for OpLocks already to this server after the
first instance of losing files. I thought everything was working ok until
today.

What is the cause of this and what is the solution?

Thanks for your help.
KT