I really don't have much in the way of a solution, but since you posted 3 days and no responses yet, I will chime in. (whispers ....... rubber bullets ) Correct me if I am wrong (probably), but it was explained once that packets can be lost during game play. Skuzzy has explained that the issue may be due to your ISP somewhere in their network (he explains it better).
Use a program called Ping Plotter and post the results or if you can identify the problem area yourself, you could contact your ISP (don't know how far you will get there).
Skuzzy's suggestions have lead me to better performance in this area...... but I have noticed that from patch to patch I have to start from the drawing board, and try turning vsync on or off, adjust detail levels, adjust texture size, and also adjust CPU (mostly according to Skuzzy's recommendations).
Finally, last night I was getting the kind of results that I had been looking for @ a month.
For those in the know, I have a question for you:
In AHII if you are experiencing noticable packet loss (rb), is it possible the distance the projectile has to travel affects its chance of being absorbed by loss packet?