KAOS, I bought a 2000 RX300 in Dec. '04 with 37,000 miles. I noticed a similar leak problem in the rear cargo area. It only happens with a heavy, prolonged rain when vehicle is sitting still. I was only able to determine that it's coming from up high near the hinges and must have been going on for awhile because there was slight rust on the bolt heads for the hinges. I took it to Lexus and they wanted $99 just to look at it. Since I have a rubber cargo mat in that area anyway and it seldom happens, I just decided not to worry about it. If you find the cause...let me know!