Desktop and Screensaver and iPhoto

My Screensaver and Desktop pictures come from iPhoto. Desktop pics Ok but when it goes to Screensaver - the computer hangs on "loading up pics" and nothing happens.

I tried to open iPhoto and I get a spinning coloured ball which does not even allow me to Force Quit or repair - I have to physically turn the computer off at the rear.

I have reset the VRam and also gone into library and deleted the screensaver plst - but no go.

When I go into Preferences Desktop and Screensaver to get rid of I have a real problem driving me nuts!

iPhoto as the source I get a coloured ball spinning which does not allow me to go to any settings to change to say Geographic Pics.

What can I do - PLEASE PLEASE HELP me as I need this computer for business! Thank you