Hi again,
There are few ways to add new mac address. And pls try to search forum and authors site for some basic question.
1. ifconfig wlan0 down
ifconfig wlan0 hw ether 00:11:22:33:44:55
ifconfig wlan0 up
2. macchanger wlan0
Current MAC: 00:40:96:43:ef:9c [wireless] (Cisco/Aironet 4800/340)
Faked MAC: 00:40:96:43:ef:9d [wireless] (Cisco/Aironet 4800/340)
3.Check
http://www.alobbs.com/macchanger4.Or don't use this option :
airodump-ng --encrypt wpa wlan0 or airodump-ng --encrypt wpe wlan0
airodump-ng -w out --encrypt wpa -c 11 --bssid 00:17:33:8C:81:77 wlan0 (or wep, for wep networks)
Or just open terminal and use macchanger-gtk :

And about "pop ups" i need more informations. If you adapter signal is pure, you can lose connection and get pop up, but that's all about pop up i can think of.