Cannot scan with canon prima mp140, but printing is ok

I am using window 10, and canon prima mp140. It was working perfectly all the while. But weeks ago, I cannot do scanning, the dialog box with MP NAVIGATOR HAS INSUFFICIENT MEMORY, always appeared. I cannot do scanning at all. Since it claim my NO NAVIGATOR has insufficient memory,  so I emptied all the folder in the NAVIGATOR, but the same dialog box still appear. What's wrong with the mp NAVIGATOR or the scanner or whatever? I checked the properties of the printer, it appeared that my printer is working properly. Thanks for any help given.