I had the same issue and never found a solution here. I didn't have a memory card inserted, so I was baffled. I could not access the screen to copy or scan, and I really needed to scan some thing. Then I remembered that the last time I scanned, I had scanned to a thumb drive. I tried putting in the thumb drive that I had used before, and viola...the message went away.
I suggest inserting the SAME card or drive you last used. Good luck.