If you try to implement the deep linking for flash/flex using SWFAddress or similar technology, you will notice the “#” character (anchor) somewhere in the URL, this is the delimiter for the interpreted URL string by the browser. If the string following the anchor change in the address bar, the browser will not change (nor refresh) the currently displayed page, instead it will try to find that anchor in it’s body. In the ordinary HTML based pages, the browser simply scrolls to the anchor somewhere in the page. For example, on this page I defined two anchors: top anchor and bottom anchor. If you click on those links, you’ll notice that the browser only scrolls the page.
Whatever, long story short, this feature can be used to navigate inside flash content as flash can read the URL and act accordingly, just by changing the URL string after the anchor. That’s great, really. The problem is that there is an issue in flash player or Flex (not quite sure) filled more than a year ago preventing the Flex preloader to show. This is not very important if your application’s SWF size is small enough, but when you have moderately large application, not seeing the feedback while preloading can actually be a real problem for your customers.
But hey, you can do something about it if it bothers you as much as it bothers me: vote for it 
More votes means more chances this bug will be fixed soon.
Please vote for this bug to be resolved.
If you are not familiar with flash based deep linking, take a look at this page :
Flex deep linking based on SWFAddress example
FANTASTIC!
Even a workaround would make me happy at this point. I have a few ideas, but none that work.