Platform: Microsoft Access 2007 on Vista

When I hit F1 for context-sensitive help within the Visual Basic editor, I
get the error: "Unable to display help." Its only explanation is that it
can't find the Help .exe file. If I choose Help from the menu and search for
the item, it usually finds it. This error happens with common items like
"OpenForm" or "QueryDef". VBA has always been very good at bringing up Help
via F1 when the cursor is on a language term. I've checked the references,
and all the correct ones are checked and working; there are no compile
errors.

How do I fix the busted link? Where and how are the various help files
managed? Is there a place (e.g., Registry) that all the VBA help files are
listed, along with their appropriate paths? How does it coordinate the
searching of the various help files, and is that something that needs to be
regenerated?