Yeah, Stephen, here are the two things I did. One was by MagicNettle:
I own a MG5650 and I had this problem too, but then I found a solution.
All I did was run the CD-ROM that came with the printer, then pressed CHANGE METHOD.
I had ticked the box where it said connect with LAN etc. from before, but then I changed it to connect with USB, the lower one.
I then did the normal settings on the printer when you start to scan (from the home screen ya know), and it worked!
I hope this helped somehow, like it did for me. 
Best of luck!
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Then this other one who didn't put their name to it:-
Been having a tinker with the scanner and ....... it worked, I scanned a document to my pc and here`s how ........
Put the document to be scanned to you PC on the platen and close the lid
From the home screen on printer,
1. Select `COPY`
2. Select `PREVIEW` .. the first button of 3 under screen.... the scanner will start scanning, and then when it`s finished
3. Select `HOME`` ... the button next to the power switch
4. Select `SCAN`
5. Select `Save/Forward` ... the first button of 3 under screen.
On the printer screen you should see `Forward scanned data to a PC`
6. Select OK button
Highlighted on the screen will be ` Local (USB)`
7. Select OK button
Highlighted on the screen will be `Doc Type -Auto scan`
8. Select either the `COLOUR` button ( If you want a colour scan ) or `BLACK` button ( If you want a black scan )
It should now be scanning your document and then transfering the image to your computer.
Seems a bit long winded I know, if someone has a better way please let us know.
Hope this Helps.
