I heard from google news that google learns how to crawl flash.
Here's the link: googleblog.blogspot.com/2008/06/google-learns-to-crawl-flash.html
yes, they can now crawl flash, but its not even as prominent as the relevance they give to PDF files as yet. Flash files are a great way to spam due to their on and off stage structure, library elements etc. At the moment, you wont be seeing any flash things at the top of the search engines unless they are really trusted and linked well. We are on the way there, but not there yet.
If your flash is on multiple pages, then yes, optimise the pages with SEO that contain the flash. However remember the site wont work on iphone, may not work for their customers (depending on market, for example, old government or people using computers with no option to install the latest version of flash due to admin rights etc).
Personally, I started my career as a Flash developer back on Flash 2 many years ago. Now I don't use it for anything apart from videos and show reels. If you can get your client to switch out of flash I would. There are few compelling reasons to stay with it for an entire website these days instead of just elements of it such as videos, banners, miniture apps, widgets etc.
Probably doesn't help but ho hum.