I have the same problem on my 2004. Took it to Autozone the other day and they said that there is a nut/bolt issue. The nut is more than likely stripped inside where the wiper is bolted down to. I have read different theories on how to fix this and I am thinking the best one is to get a tad bit bigger bolt to put in there to basically make it stick. My husband suggested to get a new nut and then put loctite on it so that it doesnt move anymore and will allow the arm to move as it should. Best of luck to you!