Been playing Sins for a few months now and I wanted to see if the community can help me on this one.  I've been having some annoying performance issues going on with large games and fleets.  Here are my system specs.

e8400 3.0ghz dualcore OC'd to 3.6ghz

asus p5n-d MB (750i) with 4 gig mushkin ddr2 memory.

dual 9800 GTX+ 's in SLI (not enabled on Sins.  Single CPU only)

During certain fleet confrontations the framerate bogs down to 10 frames a second and lower on certain occasions when certain abilities are cast.  Typically most large battles will slow a bit down to 45 fps but occasionally for no reason it will really bog down to these single digit frame rates. When this happens I check my CPU usage and it is never goes above 60 percent in most cases even during these big bog downs and I can't understand where the holdup is.  I've even tried running two 9800 gtx+'s in SLI mode and that didn't help.  I have all antivirus disabled and this only happens in large fleet battles where there are multiple types of abilities being used.  Early large battles where abilities are not all that common cause no problem but battles of the same size later in the game when the enemy fleet is more varied I run into issues.   I've played this game enough to know what it typical frames for a game on my system but it definately seems to be affected by the abliities.    I typically play medium sized scenarios and I never play online.  This happens in 1.05 and both versions of 1.09 both with and without basic graphical mods.  I typically run the game with max graphical settings at 1680*1050.    I have one particular save file that I use as a graphic test that is on the twin empire map where i take my advent fleet up against a large vasari fleet mainly composed of carriers and it bogs down to 10 fps as soon as some of the enemy ships begin casting.  I don't play vasari much but I think it's their cielo type unit.  As soon as they begin casting everything drops.  I've replayed this same save file over and over while at 1024*768 with all graphic options set to their lowest and it still does the same thing.  I've tried it with SLI and without and no matter what I still get 10fps.  Again my cpu usage is not even close to 100 percent and Sins sure doesn't tax my video cards given the fact that it's temp doesn't even raise when I play this game.  While my system isn't a supercomputer, I would expect a bit better performance with my rig.

What is the cause of this problem and what steps can I do to correct it?  I've even tried playing games with "small fleet sizes" and even then the average sized fleets of 100 ships cause slowdowns when battles commense with heavy spellcasting going on.  It's not CPU or video card related as these never get placed under a full load when this happens.  What else can I do??