[tfeld]

The A/C is always on if you use the AUTO feature, so still could be the problem. Another possibility is your sunroof. There should be drain holes in the gutter of the sunroof (there are on a couple other toyota's I have, but I've not looked at my Avalon). If those holes get clogged up with debris, water can build up in the gutter and leak into the car. Alternatively, the drain-hole hoses (which run in the A-pillar) could have come loose or developed a lead, leading to water in the car.