After 5 years of nice results, my powershot has started to show more and more often this error. It has not suffered any damage or bump, one day the batteries died while the zoom was extended and after replacing them the "Lens error restart camera" message appeared.
Browsing thru all possible forums, I found that pressing simultaneously the MENU and FUNCTION buttons while turning ON the camera, usually fixed the problem after several tries. camera works fine for a couple of days or weeks and then the error appears again.
Since the problem is fixed by a restart or reset, I believe that there is no mechanical malfunction but mostly a hardware/software issue.
Have you guys found any permanent solution apart from obviously sending it to Service or buying a new one