Here's a quick tip for ya....

If you're encrypting querystring variables and then pulling them into Flex (I think Flash will do the same thing) be sure to check your string for a plus sign ("+"). We spent over two hours this morning trying to figure out why a web service call was bombing. Turns out Flex will replace a "+" with a space (" ") so the id it was passing to our web service had a space in the middle of it which caused it to fail. To fix it we did a replace on the back end to put the "+" back in. Good times....