I'm using Backtrack 5 R3 Gnome 32 on a USB stick.

I'm currently testing ARP spoofing, password capture, etc.
arpspoof alone works perfectly after activating IP forwarding, and sslstrip and urlsnarf also seem to work fine. However when I try to implement dsniff or ettercap, or ettercap alone, my internet connection is gone after about a minute at the latest, and therefore the victim's connection too. As soon as I re-arp the victim it's fine again, but not for the machine running Backtrack. I have to reconnect to the AP in order to get the connection going again.
Does anyone how/why that is happening?