Reboot after uninstalling fmradio?

Also note that you must remove fmradio through the Application Manager; just turning off the desktop applet isn't enough. (I can't tell which you did from your post, and I didn't think to mention the specifics before.)
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Just to be clear, is it still playing out the N800's speakers? Or is it now trying to play out the AV jack, but actually only hissing?