Photoshop will open illustrator files, but as .pdf, not directly. On File > Open you should get an "Import PDF" options dialog. You can then open the file in a flattened and rasterized version; no paths, no layers, but with transparency intact.
I take it you don't have access to Illustrator, but if you do, save it to .pdf there. You could even download the trial version of Illustrator just to do this, if it is critical and urgent.
It could be that a Photoshop preferences reset is all it takes (see FAQ).
And just to have it out of the way - Camera Raw won't do you any good here. That's something