After using my Nokia N81 to make Internet (SIP) calls through my Asterisk box via a Wireless LAN, I always disconnect from the WLAN (from the Standby screen) in order to save battey. However, after a few seconds, somehow the phone connects to the Wireless LAN automatically, even when the SIP profile I'm using has "When needed". I looked at the active applications and nothing is running, except Media Player (which I can't quit) and the Standby screen. If I manually disconnect the connection from Tools -> Connectivity -> Conn. Mgr -> Active data connections, after a few seconds I see the phone connecting again.

Do you know why (and how) is the Nokia N81 automatically connecting to the Wireless LAN even when I told it not to do so? The only way I found to stop the phone from behaving like this is by powering it down, then up.

Thanks.

Did you look at the settings of Menu>Utilities>Connectivity>Internet Tel. ?
In "Sip connection", is manual or automatic connection selected?