One issue that is frequently encountered in online Help development is a Microsoft security “fix” that prevents display of content in CHM files opened from a network. Typically, the CHM file itself is opened and the table of contents is visible, but the content pane on the right remains empty.
On corporate networks, users can often get around this issue by copying the CHM to a local disk instead of opening from a network drive. When linking to CHMs on an intranet:
If your intranet Web page uses the HTTP URL scheme to link to .chm files, security update 896358 may prevent users from seeing topics in the .chm file. Replacing an HTTP file path with a UNC file path can make it possible again to open .chm files from the Web page.
For more information, see the Microsoft support knowledge base article entitled “You cannot open HTML Help files from Internet Explorer after you install security update 896358 or Windows Server 2003 Service Pack 1″ at http://support.microsoft.com/kb/902225/.