This used to be known as the E18 error in previous models.
I used this website:
and modified the steps slightly to cater for the Canon IXUS 80IS.
With the right tools this should take about 30 Minutes. It is a fairly easy job.
Tools: a small phillips screwdriver, a small flat screwdriver, tweezers, ideally a small compressor or an aerosol of compressed air ( gas will do at a push or failing that lungs).
1. Take out the battery.
2. Undo the six screws holding the facia on to the camera:
3: Remove front and back facia and wrist strap clip.
4: Remove the silver retaining screw securing the external black frame to the LCD screen.
5: Remove the black frame (on right).
6: Remove the silver retaining screw that secures the flash unit to the housing (circled).
7: Gently disconnect the ribbon cable from the flash unit using tweezers, you may find that by going straight to step 8 the cable will automatically disconnect during the removal of the flash unit from the housing. However, be aware that this cable is one of two causes of the resistance when you do remove it and go easy.
8: Use a flat head screwdriver to gently lever the clip as in the image and pull the flash unit from the top out of the housing. The ribbon cable has already been disconnected from the top right near my index finger. The flash unit will still be connected at the bottom of the camera. There is no need to remove further.
9: The lens gears will now be exposed. Mine had sand or grit in them. You can just make this out in the image. I used a cotton bud and compressed air to clean as best as I could, then carefully used a flat head screwdriver to turn the black gear anti-clockwise a few times, cleaning the gears as above on each turn. At first there was resistance due to the grit, but once cleaned it rotated fairly easily. It would be wise to use a cleaner screwdriver than the one in the image! I attemped to move the white gear but it did not play. I would have tried this further had the camera stiil not worked.
10: Reposition the flash unit and reconnect the ribbon cable using a flat head screwdiver to press it in using the lugs on the plug. This is easier than it sounds.
11: Put the battery back in and test. If you get the same error it does not work go back to step 7 and try again. It took me 2 or 3 attempts to get it right.
12: Before reassemblingI gave the camera a blast of compressed air to get rid of the accumulation of dirt etc. There was a lot around the zoom switch area (circled)
13: Make sure that the toggle switch on the rear facia is line up with the position of the actual switch on the camera before repositioning the facia (both circled). This caught me out.
14: Reassemble in reverse order to the above. Strangely enough this was one of the most fiddly bits of the operation, there are lots of tabs to line up.