Topics missing when compile HTML Help

I have written and maintain Help systems for two products in RoboHelp 5.0. Each has compiled fine in WinHelp 4 format for years. When I compile either of them in HTML Help format (single .chm file), then double-click the resulting .chm file to open it, the Contents and Index appear to be populated properly, but I cannot open a topic when I double-click one in the Contents or Index. The topic window remains blank. I would think I should be able to open the .chm file independent of any application and open all topics contained within it, just as I can with a .hlp file.

Should I be able to have access to all of my topics (about 2,000 indexed and 650 context-sensitive) just by double-clicking the .chm file? Are there specific project settings I need to set a specific way to get HTML Help to include all topics? Anything else I might be overlooking?