Drastic FPS drop since 2.3 Patch?

So I only very rarely try to run multiple instances of WoW on the same computer. I've experimented with as many of 5 instances and my system was perfectly capable of handling it...

Since the 2.3 patch however if I run two copies of WoW, the FPS drop so drastically that I can't tolerate it. I've been thinking that this has something to do with the recent addition of support for multi-core CPUs...

My system:
Quad-core Intel CPU (forget speed)
NVidia 8800 GT controlling main (24") monitor
NVidia 7950 GTX controlling monitors #2 and #3 (both 20").

Has anyone else witnessed this slow down? Any work arounds? I have asked friends in-game and they also have seen it become unworkable since the patch.

Thanks,
AndyB

Most of us have seen an increase since 2.3 Due to WoW being more Multi-thread compliant.

Can't think of any specific reasoning why would would suddenly see such a massive loss in FPS.

Has anything else changed?

Are you running your WoW Windows as "Full Screen" with Maximiser or not?

Hmmm...

Well, Like I said, I do this so very infrequently, so yes lots of things have changed. I'll have to dig deeper. Since I really don't know anyone directly that multi-boxes, but just folks who can run multiple instances of WoW for trading, enchanting, etc, the people I have talked to about this aren't really as knowledgable as the folks in this forum...

The main screen I was running windowed, full screen through WoW's default settings. The other window was windowed, but not full screen. I haven't gotten Maximizer in use at all. (Is version 1.4.1 still the most recent? It's over a year old!)

I'm definitely going to be buying keyclone as I like the idea of linking a WoW instance to a specific CPU. That and it looks a little easier than the AutoHotKey scripts I've used in the past...