So on my server that I play on with my siblings, we have a town with a road and minecart system. We all have shops. We have railroad crossings at the crossings. I was making another one then this happened. I tested it out. The minecart went over the detector rail. Powered the noteblock(more on that later) and the redstone lamps. And then they wouldn't turn off. In the screenshot attached you can see the powered redstone lamps and the detector rail that I tested with. I went into my 1.5.2 minecart rail world to confirm that it's a bug and it is. I also didn't hear any sounds when I was on that server. I had noteblocks hooked up to the detector rail in my 1.5.2 world and I heard them.