Hmm, everything checks out, voltages, boot mode pins, fuses, but we are still seeing the same boot rom code indicating that it is trying to boot over USB.
We also are not seeing any SPI bus activity for the MMC so it does not seem to be even trying to boot from the SD card.
FWIW, we have another board based on the i.mx28 that we are able to boot from SD with no problems. The same guy designed both boards and he is stumped as to why the i.mx23 board is not booting from SD having checked all the voltages, pin settings, SD card presence switch, etc.