no security in wireless connection

Just found out that my neighbour can access my ISP via my wireless 802-11g connection. And I can access via his connection...Not a good situation.
I have checked security settings in both my router and Win7 network connection.
I have checked that WPA2-PSK security and AES encryption is selected and a 8 digit network security key is current.
I have disabled sharing. When connecting the network does not ask for a network security key but connects instantly and functions correctly
I can see but cannot connect to another neighbours connection because it asks for a network security key and I do not have it.
I will appreciate any advice.

Thanks Dwarf, Your change made no difference.You may have noted that I already have WP2-PSK security with an encrypted Security key. My basic problem is that the system does not call for a security key when I connect. Disconnect and reconnect give exactly the same, I am straight into the connection with no request for a security key. When I attempt to sign on to another visible connection , not mine , the system immediatley demands a security key.
So it seems that I have either told the system not to look for a security key or I have not told it to look for a security key on my connection. I have rechecked my router setup and rechecked my network setup and I am stumped !!
I'll try anything.

talisman said:

Thanks Dwarf, Your change made no difference.You may have noted that I already have WP2-PSK security with an encrypted Security key. My basic problem is that the system does not call for a security key when I connect. Disconnect and reconnect give exactly the same, I am straight into the connection with no request for a security key. When I attempt to sign on to another visible connection , not mine , the system immediatley demands a security key.
So it seems that I have either told the system not to look for a security key or I have not told it to look for a security key on my connection. I have rechecked my router setup and rechecked my network setup and I am stumped !!
I'll try anything.

You might try going into the Network and Sharing Center, on the left side of screen you sill see "Manage Wireless Connections" where all the wireless credentials are at. Find your connection and edit or delete your connection profile. Now try to connect to your wireless connection again and see if it asks for password. :)

So after changing the key to anything else he can still connect?

Changed security key and system said it was connecting but it never did. Changed key back to original and we are back to instant connect not asking for key. Bit short of time for a few days but will totally remove wireless, reconfigure router and initiate new connection next week..Fortunately I am not concerned with interlopers as I turn off router when I am not on line.