My bad for fogging things up. Besides the epel rpm, I had also tried the (non-rpm) tar file from mozilla of the latest beta release (installed in /usr/local). That turns out to be a 32-bit version. The epel rpm is clearly 64-bit. Well if you are still seeing the same error then the only think I can think of is that elements of your install in /usr/local are conflicting with the RPM version. If you haven't already completely remove the /usr/local/ instance.