While I keep seeing the tons of useless goddamn updates major bugs and missing features dont get fixed.
One of them is the headset. Matter of fact I couldnt get any sound coming out on the earpieces ever. Any goddamn phone you buy will autoswitch to headset when you plug it in why cant you fix this.
Why is alsamixer has 50 channels on n900? Not many of them useful :/
just for the record, my N900 switches just fine from/to headset. Maybe it is some kind of defect in your N900 (like a broken headphone socket so it doesn't recognize that a headset is plugged?)
I think it might most probably be a problem at the included headset. The damn thing stopped working for me within two months. Now it's at Nokia Care and they need 10 days to replace it.
Just try with some other headset, and if it works, then it is the problem of the headset and not your N900. Else vice versa.