Photoshop CS problem


I've been having a strange problem with Photoshop CS and I can't figure out why. I can not open a file by double-clicking it. It will launch Photoshop but the file won't open. I also can't switch between Photoshop & Image Ready or edit a linked image in Indesign. I tried reinstalling the software and trashing prefs. It used to work but I can't figure out what I did to screw it up. Any suggestions?