I have the exact setup as the OP minus 1 gig ram.

I run 3 accounts at 1680X1050 windowed w/full graphics settings in wow on all 3.

I average 40-50fps in Shatt and SW and 50-60 outside of the city. I even hit 60 FPS in the city at some times. Someone was bitching in general chat about low framerates and I mentioned I had 3 accounts high res full graphics sitting at 60 FPS. This was in SW during the weekend.

I've never used Keyclones options to reduce the FPS of slave accounts. I dont use Keyclone for multi screens. I keep a very very clean computer, every 30 days I redo my comp with a hard drive clone, get the latest updates and re-clone.

My specs:
Main WoW running in C: 2 slaves running in partitioned e: drive.
3gig cheap Ram
GeForce 8800GTS 512
WD 500gig SATAII Drive
Q6600 processor
PK5-E Asus MB
Vista 32 home pre

EDIT: Try and run both with NO AddOns and see what FPS your getting.... also, if your ok with this, try and yank 1 gig of ram out of your box, 32 bit OS only supports 3gigs. There MAY be a conflict in there somewhere, i dunno, not an expert.