FF9 and PS CS5?

I know the title of this will probably make some of you cringe, but I still use Photoshop CS5 for a variety of reasons. I usually use FF separate from the program on finished images but I was recently trying to use it as a plug-in but can't get it to work. This is the error message I'm getting:
"<class XFW::StateError> The control <class Controls::Control>@000000000B340F70 has no window handle."

Does anyone know what might be causing this and if it's fixable? I have the 64bit version installed and I have the FF x64.8bf and .config files in the Plug-ins folder. If anyone has any ideas, I would greatly appreciate them!

Two caveats:
1. I was able to use FF7 as a plug-in with CS5 before, I don't remember if I was successfully able to do it with FF9
2. I built a new desktop over the summer, and transferring CS5 over (it's a legitimate copy) was a pain because I was missing the disks. So there could well be something going on with the way CS5 was installed.