I had this problem when copying a large (50GB) disk image file (Macrium Reflect) from my Flash Drive to my computer.
"Out of Memory. There is not enough memory to complete this operation."
I had more than double the disk space, had about 12GB of RAM so the error message didn't make much sense to me. But this was largest file I could remember copying so thought the size might have something to do with it.
I downloaded Teracopy and tried using that to copy the file; it too failed but gave me a much better file error message: "Open Error: Access is denied"
I check the file Security Permissions (right click Properties --> Security) and indeed the current user did not have Read Access. I add the permissions and it copied fine.
I am guessing because the file was created from a Boot Disk perhaps it didn't know which user to assign the proper NTFS permissions to (although I think it could just leave it open to everyone?)
Also I think Windows 8.1 has a bug when it tries copying a file with wrong file permissions it falls through and displays the wrong error message.
I had this happen today while copying files off a SATA drive connected to a USB3 dock via an adaptor. When I went to check the drive for permissions (as per Nathan's answer) I found that the drives had vanished. I unplugged and replugged the hard drive and it worked fine afterwards.
