Hilft dir allenfalls diese Antwort (war zwar in Zusammenhang mit dem K700, but who cares?) von nextlink?
"It is strange behaviour with K700i, since we have some customers that have updated their phone and have no problems. Anyway, we had a customer last week with a new Sony Ericsson S700i that had similar problems. The problem with that phone (probably the same software as new version of K700i) is that the phone has a software problem when it tries to connect as a master to the headset. This means that after pairing when the phone rings it tries to connect to the headset and it can't do that since it has problems. Solution to this problem is to do two things:
1- change the bluetooth settings on the phone, not to be visible
2- erase pairing on the phone and pair it again with the headset. After pairing
initate connection from the headset, and the problem should be solved. If this
works then the user has to initate connection from the headset and not let the
phone try to do that, meaning that when the connection has to be initiated
before the phone rings and the connection will not be lost as long as the phone
and the headset are in the close range."