Have you installed the Photoshop updates?
And are you trying to open from the Open dialog, or double clicking in the Finder?
Did you install any third party plugins? If so, have you tried disabling them?
I havent done anything to it at all. Just got it last night but I've had it twice before. I just go to File>Open then select the file and it comes up saying that the file was not found.
Then you need to download and install the updates.
It sounds like something may be broken with your install (missing files).