The striker (the part that's on the window) doesn't line up with the latch(the part the striker hooks on to). Take a look at where the striker hits the latch. If it hits the outer lobe of the latch you must very carefully grind it down (with a dremel or a file) until the striker clears it.Obviously the striker is supposed to hit the inner lobe of the latch forcing the outer to wrapping around it locking it in place. If you can't see the striker hitting the latch, look at the latch and see if there are wear marks on the outer lobe, or if the window hits really hard, then you'll know if this is the problem. Let me know how you made outor any ? e-mail me (tombencze @aol.com) Thanks.