Is it not already? I thought Flash was pretty much a dead technology five years ago, I've certainly only designed in it once in the past seven years, and that was for some dumb banner advert that I could now do with jquery.
Depends on what you're using to process the form page. How I do it is pass all the form variables along to the error page and re-insert them into the form items as values
value="<?php echo $_POST["formitemname"]?>"
hope that makes sense
I'd also recommend looking up the software Forms To...