If that is the os7400 then I've seen that when you don't initialise them properly.

Backup the programming.
Clear the sd/mmc backup (mmc815)
Power down,
take out the mp40,
turn off the memory switch
Turn system on
Wait for it to start
Turn off
Turn on the mp40 memory switch
Turn on system and restore backup

That usually fixes things like that with 7400's