Well, I just switched on my Canon 40D and saw this error "ERR 06: Self Cleaning Sensor Unit Malfunction. Consult with Canon Service Center" on the screen. Wait a minute, what is that I did wrong which lead me to this error. I tried to recall everything that I did in past. On Sunday I took almost 1300 pictures from Chicago Marathon 2008 and while downloading those to my laptop I didn’t follow the instructions given by Canon.
Canon says whenever you use the usb cable to connect your PC/Laptop then turn off the camera before plugging-in and turn off before plugging-out. Turn the camera on only after you plug-in the usb cable. I guess I didn’t follow the instructions properly. I am not a master in photography or in using this camera. I am just a novice so committed to make mistakes here but each lesson will make me better as a photographer.
Here is a solution which I found from this forum, it is a long posting there so follow my instructions and see if it works for you.
Good luck guys! Let me know if this works for you.