Alpha AWUSO36H 1000mw + aireplay-ng

Using the above card and aireplay-ng -p0841 command in backtrack 4 final does not increase my packet data. I am doing it clientless and in backtrack 3 final using same command and card works great (also clientless), data packets increase atleast 500pps!!

So my question is can anybody get the aireplay-ng -p0841 command working in BT4 final? and why does it work in BT3 but not BT4?

Has anyone got another way to do this clientless on WEP? Just strange why it works on BT3 final But not on BT4 using same technique and card etc.

I am new to backtrack and have never used backtrack 3 so cannot comment on any differences.
What I can comment on is that the 0841 attack works for me using backtrack 4 with the same alfa card.
I used google to help me along the way.