Screen is black while taking picture.

Sounds like you just accidentally pressed the DISP or DISPLAY button on the back of your camera. This turns the screen on and off in photo mode to save batteries (you'd then use the optical viewfinder in its place). Just press the button one more time with the camera turned on.

When you say doesn't work, can you be more specific? Are you seeing a black screen? If so, have you tried pressing the DISP or DISPLAY button on the back of your camera?

So, stop trying to connect the camera and get a card reader for downloads.

try the display button if thats not the problem, then ccd lens sensor went bad and need to be repaired by canon http://www.usa.canon.com/consumer/controller?act=ModelInfoAct&fcategoryid=183&modelid=14904#SupportDetailAct

Could be ccd problem. These were common with this type of Canon camera. Download Canon pdf file re these faults.

Don't fret, there's nothing wrong. You just accidentally pressed the DISP or DISPLAY button on the back of your camera. This manually turns your screen on and off to save batteries. Press it once more to turn it back on.

This is somthing your going to have to get fixed at a shop

If you see black margins above and below your pictures, you may have the camera set in Widescreen mode. Press the Func/Set button and see what icon is in the lower left corner of the LCD screen. If you see a "W" there, scroll down to it and you will see the other size options available. You should have L, M1, M2, M3, S, and Postcard as other options. Selecting any of these will make your pictures look 'normal' again.

The following blog outlines some repair options for a lens error. They won't work for all cases, but they're worth a try if the camera's no longer under warranty:

http://camerarepair.blogspot.com/2007/12/fixing-lens-error-on-digital-camera.html

Then it sounds like there may be an error with your CCD (what comverts the light going into your camera into a digital picture, like digital film). even if your warranty is expired canon may still repair this for free. Contact canon at 1-800-OK-CANON and explain to them the problem and that you think the CCD may be defective.