Has anyone come up with a solution. Siege battles with fire arrows, onagers or more than one battering ram really takes a toll on my FPS. I dont really think its my PC I have uninstalled/reinstalled drivers, and tried changing settings on my video card and in game but nothing seems to work at all. I have heard about others with comparable systems having no trouble at all and some with lesser systems having no trouble at all. Is this my error or something related with the game code?
Here are my specs:

AMD Athlon 64 3200+
ASUS K8V SE Deluxe
ATI 9800 Pro 129
1 gig Corsair XMS