Using 11.19 stock on a Nexus One, although I have noticed this bug since I have used MIUI and the FM Radio. If I am listening to the radio and receive a text, email, anything that prompts a system notification sound, the radio audio will stop (much like it would with any music player) but after the notification sound completes, the radio audio does not start back up. To restart FM radio audio, I must open the FM app...select On/Off 2x to turn the radio off and then back on. The audio will then start working again. A nice fix would be have notifications play through the phone speaker whilst headphones are plugged in and audio is playing... Not a huge issue, but figured I would report it since I consider it a bug.