I have a 1995 Chevy Astro van that leaks water.

I have a 1995 Chevy Astro van that leaks water from the inside every time it rains. I had the windshield replaced, but it didn't solve the problem. Several months back I had water collecting somewhere around the back hatch. Every time I would open the hatch after it had rained, I would get a wall of water dumped on my head! It hasn't done that in months, but now I have water coming down from where the headliner meets the windshield. I have gone around the van to check the rubber seals around the doors and hatch, but everything looks fine. Has anybody else had this problem, or know what it could be?