slow down with rain effects


Youth Team
HI all.
Ive noticed my game slow down to unplayable levels when the rain effect is on during a game. When the weather is clear the game runs liek a dream. This has only happened since i installed 8.12 catalyst driver. I have since the problem began uninstalled this driver and have used 7.10 instead. I have no profile settings activated for this game to casue the issue.
My setup is

asus a8v
939 388+x2 chip
2gb ram
xp sp2
x1950 agp radeon
dx 9.0c - latest update.

I run the game usually at 1290*768 or the closest to that in 16.9 . problem not really existed before. a, running at 1024 now and there is little or no difference , the game still slows with rain on.

I have v-sync checked .unchecked the slow down is even worse.

ANy ideas soutions etc most appreciated.,

Cheers in advance.