Photoshop CS6 beta 64 bit, Windows 7 Pro 64 Bit
Working on PSD file, then opened second image from ACR. After choosing 'Open Image' from ACR the second file appeared onscreen, with the first image behind it in psychadelic colours.
Zooming caused the second image to leave ghost images on the psychadelic background.
Unable to work in either image, had to close down using Task Manager.
Sounds like it could possibly be a graphic card issue. Have you updated your drivers recently? Up to date drivers usually take care of issues like this. You might even want to reinstall the drivers.
If that doesn't work, make sure to post your system info as a reply. System Info from Photoshop
Europe, Middle East and Africa