@dvb
Near that transistor there is the BB5 Baseband "Rapuyama" IC.
If i was in you, i would try some kind of pressure against that IC and if the phone works again, maybe a quick heat up with a hot air desoldering tool could help without a complete rebailing of the bga.

Take care, this would be my attempt if my N900 would be in that condition, i don't want to be responsable of further damages on your device