FPS on second monitor

Hey guys, I just installed my new ati 4850... what a beast! Only I'm having problems when i move wow instances to my second monitor. As soon as any part of wow goes there it stutters like crazy, I've changed the resolutions so they are equal, refresh rates and such. I should add i didnt have this issue with my old nvidia 7300, though im sure its not to do with the graphics card but some minor setting somewhere.. any ideas? Sorry if this has been answerred elsewhere, I did search around but, FPS is a common subject here >_>.

With Dual 8800GT cards, if I do dual monitor in Dual View mode (as opposed to horizontally extending desktop) I get crappy FPS on both. I can run 2 instances on one monitor in windowed mode, running the video in SLI mode, and maintain 60 FPS all day. Check you video card documentation and see if they discuss various modes and performance rates for each mode.

make sure that the wow window you are moving over to your other monitor is completely moved. In the past if i have the window shared across both monitors it staggers and such.

It's completely moved :/... have done a little research, seems it could be down to me having a nforce sli chipset motherboard with the ati 4850.