If CS3 use to work the first thing to try is resetting your Photoshop Preferences. Start Photoshop by clicking on its launching Icon. Then immediately press and hold Crtl+Alt+Shift. If you do the in time Photoshop should prompt ask if you want your preferences deleted.Reply Yes. See if it then starts up...
Hi, thanks for the reply! I did that, and recieved the message "Delete the Adobe Photoshop settings file?", to which I clicked Yes. It then attempted to continue opening and gave me the same message as before.
And it was working just fine until this evening. Thank you for trying to help, I appreciate it. I've also attempted uninstalling and reinstalling it, but no dice.
Hey to anyone reading this, I am posting this in case other people run into the same issue as me.
If your CS3 has stopped working, uninstall all tablet drivers (in my case, this was the new intuos tablet and my old bamboo), even if they have never caused an issue before. This fixed my issue, and I was able to reinstall the intuos again afterwards and everything opened just fine.
Thank you JJMack for offering a solution too!