N900 Operator lock on Sim free phone???

Question

Hi.
When you go into settings, at the very top bar there's a settings drop down button.  I have 3 options there:
Restore original settings
Clear device
Enter code to remove operator lock
Why would a sim free phone bought from a nokia retail outlet store have an operator lock? 
I received a txt message from vodafone back in june that said to restart the phone to receive updated vodafone sime menu service.  I dont know if it worked because i'm not sure where the sim menu is on the n900 but i'm curious if this is what has introduced the menu options above.
I should mention at this point that when i was in the US earlier this year, i was able to stop my phone looking for a gsm signal and concentrate on wifi only.  Now i can't seem to find an option to turn of gsm.  When selecting the network from the phone menu, i only get Dual, 3G and GSM.  i don't get the wifi option anymore, hence me asking if this operator lock has interfered with it
Has anyone else got this and if it wasn't vodaphone, what is this operator lock?
Thanks in advance
Bagz Rules

Answer 1

here's some stuff you can try without installing extra bits:
1) stop it using 3G/2G data, wlan only:
settings -> internet -> Connect automatically -> WLAN
It won't stop you manually connecting to 3g data (if you specifically select a 3G connection from the "internet connection" item on the desktop menu), but it won't do it by itself
2) Stop any/all GSM/3G activity
Easiest option, take the sim out! Instant tablet mode no GSM for data or calls!
Another trick is possible if your phone asks you for a SIN PIN number when you turn it on. There's skip button. If you press that rather than entering your PIN, the phone functionality is disabled If you try and make a call, it will ask you for your PIN again)
The Tablet mode switcher app is pretty neat, though