Photoshop CS1 not opening files

I'm running photoshop CS1 on OSX 10.4.11. It used to work fine but after a recent system re-install I can now only open files via the file/open menu - double clicking on a file or dragging it on top of the Photoshop app icon doesn't work (it just opens photoshop, but not the actual file).

I'm presuming there's a pref file or something that I need to drag out of my old system into my new one?

I had that problem a while ago, I think resetting photoshops prefernces cured it, but am not 100% sure

Hold down Command, Option, Shift while starting Photoshop. A dialog box will appear asking if you wish to delete the preferences file.

thanks for the tip. Alas I've just tried it and it makes no difference

I don't know how to fix this but if no one else has any suggestions here, you might try the Adobe Forums if you haven't already. They are large and sprawling but there is a search function. In desparate times, I have just scrolled through umpteen posts.