The need for clear, SE-friendly navigation is obviously not a subject the designers of flash menus would like to discuss since buying the second programme virtually ensure that buying Sitemapper will be a waste of money.

Having bought both I wonder if the solution would be to include "invisible" HTML navigation in addition to the visible Flash menu.

If not, would someone make me an offer for a redundant copy of Flash menu?

Yes, you should include an HTML menu in addition to your Flash menu for SE visibility!

There's no need to make it invisible, though. One of the most common ways to do it is to include a complete HTML menu in the footer. Check a few sites on the web and I'm sure you'll find that such "footer menus" are very common!

I just learned this as well. I did what Per suggested, made a very plain text link menu at the bottom of the page.

You should not comment out links (make them invisible). It will hurt your SEO.