maybe there's an "answer on flip" or "answer on (physical) pick up of phone" setting?
aaah, how do I check that again?are any of those motion settings enabled?
maybe the proximity one is, and you have a bad proximity sensor?
vshan said:download a logcat application from the market and check the system logs just after this happens. maybe they will provide some insight.
I think you can also answer with a voice command.