Truthfuly that will only half fix the problem. Anyone with enough savey could simply download the swf from the site, play it as a standalone, and click forward to go through the game.
Of course that only really helps them if it provides them with infomation which is helpful to beat the previous level.
There aren’t too many games where this would be a problem, I think. If the scores are totaled on the server from the server based game, then they should still remain unchallenged since the player had taken the swf out of the loop.
There could be something whereby a portion of a map were revealed as the player progressed through the levels, in which case he might be able to divulge critical information about the game by downloading it. In that case, you have to be a little more tricky in how you design things.