The tape deck on my 2000 RX300 seems to not like cassettes. I haven't put a cassette in it for who knows how long, but just got a cassette adapter for my iPod. I have a good FM transmitter, but in a crowded market like Chicago, a good station is hard to come by, and when it does, the quality is not so hot.
I put the adapter in, and it keeps on changing sides automatically. This gets annoying since it happens 10 times a minute. I just want to have it stay on one side so I can just play my music. Before you ask, I've tried both sides of the adapter and get the same results. My last car (Chevy Impala) had a feature that was basically "tape adapter mode". I would guess that Lexus would have something similar.