Unable to edit copied layers in Photoshop CS

I'm having an issue with editing layers copied from one file to another in Photoshop CS. It seems to be essentially locking the layers and I can't figure out how to unlock them. I've tried duplicating them, renaming them, and resetting my tool preferences (I'm desparate and frustrated). They are in the same mode. This also tends to be an issue with opening a .jpg or .gif file and trying to edit it. Does anyone have any suggestions on how I can fix this?

EDIT: OK, it seems the issue was my computer had the user permissions set for read/write only. Once I changed it so that all users had all permissions I was able to edit it. Glad I didn't start yanking hair yet!

Huh? It could also be that you need to double click on the layer too. You, and NOTE: READ / WRITE permission is about all the acess that users get, besides execute!