yeah flash only sites are a nightmare for
SEO professionals.
I'd say your best bet is to use flash on the site for some elements like logo, banners, menu and have all the site sontent text be on the page in text format. It'll make the search engine robot happy :)
if you make a nenu in flash then it's a good practice to include a "copy" of the menu in the bottom of the page in plain <a href links
hope this helps