I'm no expert on using SPI but looking at the AT93C46 datasheet have you setup the SPI interface to suit this chip.
The datasheet says 2Mhz clock but SPI defaults to 4Mhz (look here http://arduino.cc/en/Reference/SPI
) so put a SPI.setClockDivider(SPI_CLOCK_DIV8) to drop clock to 2Mhz. You need to make sure the SPI mode is correct for reading/writing bits on rising edge of clock pulse (SPI.setDataMode(SPI_MODE0) ) and the bit order is correct MSB to LSB (SPI.setBitOrder(MSBFIRST) )
The final hurdle is the CS signal seems the wrong way round, normally CS is HIGH and pulled LOW when your talking to the device but the datasheet shows the opposite of this. You could maybe overcome this in software by using a different output pin to slaveSelectPin for CS, set it to HIGH just before reading/writing to AT93C46 and then set it LOW after.