My son and I have our PC's networked using two Belkin USB network adaptors.
When either of us select the site survey tab from the Belkin USB WLAN monitor, there are now two entries. They have different BSSID numbers and signal strengths. Under the SSID heading, WLAN appears as normal plus the additional entry which is shown as belkin54g, the latter having the lower signal strength.
Couuld this additional entry be the reult of somone very close using a wireless network, which could of course lead to potential security issues.