Parent menu item does not work

Parent menu page should come up with one click when "Go to the page on double-click" turned off.

No it shouldn't. The double-click option means that the link works as a normal link /at all/, which since the single-click behavior is dynamic expansion, can only be done via double-click. If you turn that option off, then the link behavior won't work at all.

If you want an easier way to access the parent menu than double-clicking, then you should turn on the "extra link" option, which will place an italicized page link directly under the option.

Alternative usability features are being planned for Drupal 7, but you currently only have the choice between "double-click", "extra page link" and "not at all".

I disagree with this design, as it breaks common assumptions about link interactivity. Double clicking is a desktop action, not a web action, and I can't remember the last time I double-clicked to activate a link. The accepted design pattern for double-clicking is to open an application or a file, not to load a page. My users have no idea they need to double click the link, so they assume the link is broken, and the extra italicized link is redundant.

I understand that a single click won't fit in this module's design, so perhaps a rethink is in order.