FMCB does work on all my generic memory cards, I have like 8 of them and all work perfect...
I would first try cleaning the memory card and MC slots and usb devices and usb slots.
use rubbing alcohol and qtip, make sure no metal stuck in there...
try other slot for memory card or usb device.
what it sounds like is bad or dirty usb slot or short in usb system. or your usb device is bad.
could also be memory card slots. You might have to open the ps2 to clean those.