I had this behaviour a couple of times so I guess it is a bu^C^C feature

If I switch the FMradio app to full screen, then enable the speakers, all is ok. Closing the full screen app and stopping the playback on the applet will result in no sound through speakers until the next reboot, unless I switch the fmradio on again and switch to headphones. The only thing turning on the speakers is the FMradio. (of course I'm talkin of when I already disconnected again the headphones )

Guess it has something to do with the way headphones/speakers are managed by the fmradio app, especially with the fact that it has to work with the headphones connected, but through the speakers.