Issues have arisen and users have reportedly lost data when saving files to Microsoft's Home Server. Microsoft has confirmed this and has posted a support document.
The support document, confirms that there is a flaw in Home Server and lists which programs may cause files to become corrupted when saving to the server.
To date, no fix has been forthcoming from Microsoft, who warns users to make a copy of files related to the affected list of programs, before storing them on the server. In fact, Microsoft warns against using these programs at all.