EC Software the makers of Help & Manual, which I use for my documentation, have released a free utility to combat the problem with viewing compiled HTML (CHM) files over the network. The problem was introduced by Microsoft Security Bulletin MS05-026 which had the intent of protecting Windows users from security threats posed by these files.
The fix involves complicated registry changes. The utility created by EC Software makes this change easy.
http://www.ec-software.com/products_hhreg.html