What do you have connected to the MXI 2, or are you booting without anything connected?
Were these MXI cards recently working on another system, or was it sitting on a shelf for a long period of time, etc?
The first thing I'd suggest you try is resetting the EEPROM to defaults. If the configuration stored there isn't valid, or isn't compatible with the motherboard you are using, resetting to defaults will often clear it up. Directions are on pg B-3 (pg 94 of the pdf) of the Reference Manual.