This is strictly a guess here, but I would think you are in trouble because you have a Macintel computer. I would expect Safari to be compiled for the Intel CPU, but the Runtime Engine is compiled for a PowerPC chip. The Macintel computer can handle code for the "other" cpu in an emulation mode, but not when you have Safari for one CPU trying to access a plug-in for the other CPU chip. That seems like something the emulator would not be configured to handle, but I could be wrong.
Bart