I found a solution by blind chance
Today my Canon A75 failed totally. The monitor was flickering, magenta lines over and over (as you can watch on youtube), video and pictures. Playback and menus were ok. A sensor problem? NO!
I tried a reset, known from some other devices:
I turned off the camera, pressed the release button fully down, and turned the power on (in record mode).
A red dot appeared in the upper right corner for some seconds, and the monitor was back.
Bingo, my camera is back to service and works fine again!
No sensor problem, the software seemed to be confused.
This reset is not documented by Canon!
Hope it works with other A75.