2 PC low fps

My computer spec is i5 2500k, 8Gb Ram, GTX670. It runs wow at 60+ fps on ultra. When I run 2 windows via isboxer it drops to 6-9 fps, even on VERY LOW, which is abnormal for this computer. Even my older HD4870X2 which turns off crossfire in windowed mode managed to run 2-window layout on 30+fps and 60+ fullscreen on ultra 1920*1080. Ok, then I decided to run both of my accounts on different computers. My notebook is core i5, 6Gb ram, GF 555M, it runs ultra on 40+ fps 1366*768. But, again, when it comes to inner space each of computers running just one copy of WoW manages only 10 fps on low. So, this is not my poor hardware, this is something with your program. And running 32-bit on 64-bit sucks, too. Any ideas?

P.S. My Inner Space build is 1.11 (5670), Isboxer is also up to date. I didn't use them about 4 months and now when I updated them I get this kind of #@$%.

[lax]

The following guide is specifically to help you with problems like this one:
HOWTO: Tweak your framerate

One thing you can try that isn't listed in that guide, is to try WoW's DirectX 9 renderer instead of DirectX 11. Some people have reported that WoW performs better in DX9 mode than DX11 mode for them, since a recent WoW patch. You might also double-check that ISBoxer is using the same mode as when you're not using ISBoxer (there is an option for this in the game's Advanced video settings, so you can check it with and without ISBoxer)