vtest27@mail2web.com declared for all the world to hear...
> If the phone was supplied by Vodafone, and it won't work with another
> SIM card, this is likely to be because the phone is locked to the
> Vodafone network.
>
> To unlock it, you'll need a Network Unlock Code (NUC). Vodafone can
> supply this.
>
> I'd suggest getting in touch via the web form at
> www.vodafone.co.uk/contactus. Make sure you include the make and model
> of your phone and 15 digit IMEI number (found by keying *#06# SEND on
> your phone).
>
> In the meantime, it's best not to attempt to enter anything else, as
> entering the wrong code several times can permanently block the phone.
>
> If the phone is less than 12 months old, there will be a charge of
> =A319.99 for the code.

Network-locked sonyericsson phones will display "insert correct SIM".
The message described is referring to the phones own lock code,
defaulted to 0000 and documented as such in the manual.
--
Regards
Jon