We have had some support tickets regarding users not being able to see the Ostendo Reports folders from Windows Explorer, however they can see them from the Ostendo Report & View Developer.
After some investigative work on this it appears to be related to Microsoft virtualising directories.
Please refer to the attached links for more information:
http://www.jondavis.net/techblog/post/2008/02/05/Beyond-Disabling-UAC-Disable-Virtual-Store.aspx
http://www.interworks.com/blogs/dsmith/2011/09/21/disabling-windows-7-virtual-store