I'm not sure. The poject is quite complex.
It is an interface between two protocols (PS2 serial, and propietary protocol). It just does not work... I'd have to use a logic analyzer to see in detail, but I don't understand why a 16F84 does not work using same code as 16F628, when not using any of the extended capabilities (not internal oscilator, not extra i/o pins, no extra memory registers,...)
Just wondering if I missed something... but I can't see it now.
About the fuse settings, I'm not sure if you mean the configuration word. It is Ok i think. No watchdog..