This message means the memory capacity of the unit has been exceeded. The amount of memory used depends on the amount or type of data on the documents being copied. If you get an "Out of Memory" message, press Stop/Exit to cancel scanning.
If you get an "Out of Memory" message while scanning a subsequent page, you can either press Mono Copy or Colour Copy to copy the pages that were scanned so far, or press Stop/Exit to cancel the operation.