Kaybee

I have exactly the same problem with my year old 250C. Three times back to the dealer with no reason found but a number of modifications apparently done. The dealer reports that there have been no similar complaints, at least in Europe. I have made a number of audio recordings of the noise which appears to be on the right hand side of the car and appears to be loudest around the side windows. Last visit to the dealer ended with them reporting that they could not hear the noise any longer so I am now ready to confront them with the audio CD's. I am not sure that it is the roof latch mechanism. From the CD's I hear a very similar noise as the door locking mechanism latches when the speed rises. Like you I could begin to like the car but I have been so disappointed with this my first Lexus that I have only done just over 3,000 miles in the year since new.