Camera is on but LCD screen and viewfinder are both black

Quite often, the ribbon cables lose their connection and need to be re-seated. If you're brave enough and have the dexterity and enthusiasm for such things, pull it apart, noting which screws go where and disconnect and reconnect the ribbon cables from the lens unit. It's worked for me in the past.

1. Press display (DISP.) button to turn the display on Do this when your camera is on and in shooting mode. This should fix the problem. I had to try it a couple of times before it worked.

You either have a bad CCD or aperture. Look down into the lens when the camera is on, is there a small opening at the bottom? If theres a small open circle at the bottom, your CCD is bad not the aperture. Its very possible your camera is covered under a huge CCD recall but I cant figure out this site so Im not sure what your model is. If its F717, Sony will fix it free.

www.darntoothysam.com

1. Press display (DISP.) button to turn the display on

If your battery is fully charged -put camera on video recording mode. Record with voice. When played back and the voice can be heard but the LCD screen remains black or distorted the CCD is bad. Sony will replace for free up to Sept. 08. You can place a service repair order at http://esupport.sony.com/perl/select-system.pl?PRODTYPE=38,33,7,37,25,39,53

Thank you to all that posted. I ended up calling the manufacturer, can't remember offhand who it was and they shipped me a brand new camera. The customer service person told me this was a common problem with these digital cameras.

In the past I went through every option on the menu screen and no luck. Today I pressed the DISP button in the lower left area and now its fine. Wierd! Hopefully it won't go out tomorrow.

This sounds like it might be a defective CCD imager. If so, Canon should fix this for you for free, including free shipping both ways. This is regardless of your camera's warranty status. Please check the following two links for more info:
http://camerarepair.blogspot.com/2007/11/canon-digital-cameras-showing-black.html
http://www.usa.canon.com/consumer/controller?act=PgComSmModDisplayAct&fcategoryid=225&modelid=13390&keycode=2112&id=29819
Applicable cameras include:
A40, A60, A70, A75, A80, A85, A95, A300, A310, S1 IS, S60, S200, S230, S330, S400, S410, S500, SD100, SD110