"The problem could be dirt, debris or a dislodged lens. Here is a great site that may help you getting it cleaned and working again. Of course there is also the possibility that you truly have a lens error.
""ZOOM LENS
ERROR
Movement of the lens barrel does not end within the specified time.
Cause and Probable Faulty Part:
MAIN PCB ASSm'Y
OPTICAL UNIT""
Now if you are inclined to fixing your camera, you can download the service manual from here or use the guides from here Canon PowerShot SD750 Repair Good Luck."
There is a rubber foam washer that separates the lens from the casing in the camera. I have taken a few apart and have found parts of these washers dried out and destroyed. Particles from these washers will get into the cameras lens and obstruct it, causing malfunction and failure. Some of these washers can decompose from either dry heat or other conditions.
