I saw it. Okay it can be many things, my guess and from my experience the ribbon cable has caused similar symptoms. Sometimes when its too long or even slightly torn it causes problems or interferes with other things within the mpc.
Before you upgraded it what drive did it have? (floppy or zip) Was it like that when you got it?
That error is common w/ floppies and zip drives usually turning the mpc off fixes the issue but the way the numbers and f1 f2 f3 etc are mixed in. Its strange.
If you have one try using 1 gig Ultra 2. Anything above 1gig doesn't work on the card reader for the XL. And sometimes its picky with specific compact flash cards. Another thing would be to check the inside very carefully. See if anything is out of the normal.
Another suggestion would be upgrading the OS. On most XL w/ upgraded card readers you would need the OS upgraded swell to 1.20. Sometimes it works with 1.14 but its rare. You can find the OS upgrade on AKAI'S website.