Context-sensitive WebHelp generated through RoboHelp 11 using URL works locally but not online

Using RoboHelp 11 to generate WebHelp that's called through a URL, for example: http://domain.com/folder/subfolder/index.htm#bookname/helpTopic/helpTopic.htm (where "bookname" is the folder containing the subfolders for each individual help topic, each with the same name as the individual help topic, as imported from FrameMaker).

The help content is posted publicly to the WWW.

When I test the link locally (from my C: drive), it works.

When I call the help topic from the application, it pulls up the frame for the help set, with a 404 error displayed for the help topic identified through #bookname/helpTopic/helpTopic.htm.

However, I can click the link to the help topic from the TOC in the help set frame, and it pulls up the help topic correctly. 

The main help set link (http://domain.com/folder/subfolder/index.htm) works fine.

The help content for a prior release, generated the same way, works. It's just the new release that is generating the 404 error for the context-sensitive link using the #bookname/helpTopic/helpTopic.htm suffix. So I must have done something different for this publish, but I can't see what it is.

Any help greatly appreciated.