I have Canon optura Pi (I think since 2001). Now periodically I have a problem - sometimes focus goes down and picture become blur. Later on focus returns.

SOURCE: blurred pictures

Batteries don't play a role in it. Maybe it has slow focus. Try to push the shooting button to only half of its full push, wait a while until it focuses an then shoot by full press on the shoot button. You can also check if you have not switched on macro settings (flower in frame). If you do, turn it off.

SOURCE: I have a canon ixus

Believe it to be a camera fault. Reason: zoom feature makes the lens extend for telephoto work, therefore, the autofocus feature should be working at any distance you set the lens for and your shots should be clear. Could be an autofocus problem or the lens and CCD are misaligned at the telephoto position. Have the camera checked by a qualified repairperson. Get an estimate first. You may want to ask this question at the Canon website also.  

SOURCE: My canon 1100 powershot camera

Have you checked for a fingerprint on the lens?