loosing network conectivity when using linux in Parallels

I have installed BackTrack linux on my Parallels.
Im using a macbook air mid 12.
i set the networking device in the parallels to bridged, so i have both my mac & internal IP as in my mac.
once i start using arpspoof in parallels, internet connectivity is lost in my mac.
in linux it remains..i can ping google or whatever.
anyone knows a solution?

yes, i have installed them

i do, and it works as it should
i do arpspoof -i eth0 -t target router
where eth0 is the correct card, target is 192.168.178.99 which is my test computer and router is the correct ip too , 192.168.178.1
if doing arp -na on the target computer, it shows my mac address for both my ip & gateway ip
so why it screws up my internet?