Network Key keeps changing

I can not access the internet because of my security settings. I try to connect to my home network and it says there is a problem with the security settings. I then click on security settings and type in my network key and push ok. I try to connect again and it takes me to the same place but the network key has gone back to what it was before. It will not change. I have tried restarting computer and everything. It is very frustrating . Does anyone know what is happening?