|Are you using encryption for your wireless lan?|
Hopefully you do.
Otherwise, your wireless lan is open for use to everyone. And everyone can connect to your router settings by using that ip address. Also if you haven't changed the default password, there is a list in the internet, where everyone can get the default password and then can access your router and change the settings.
The original poster should always write the last response !!!
Let us know, if the problem is solved !!!