Stop clicking back and forth between the buttons and the X
icon.
OK, that's a half-joke.
If you haven't installed the 7.0.01 upgrade, you should do
so.
Another step that might help is to generate for Internet
rather than local/intranet deployment. If the TOC, index, search
and/or glossary files are big, RH breaks them into more (smaller)
chunks for Internet placement. My hunch is the browser gets
confused when you click while it's opening a bigger chunk.
This leads me to another, more serious recommendation: Wait
for the nav pane to finish loading before closing it or moving
between components.
Harvey