When I try to save an image as a JPEG, in my CS5, it says "File must be saved as a copy with this selection". This never used to happen. Does anyone have any idea as to what I can do to remedy this? Thanks.
That usually means either your jpeg has layers and is not flattened or has some things like alpha channels, spot channels etc that are not supported with the jpeg format.
In the save As dialog, the yellow warning triagles are next to the things that the jpeg file format doesn't support or save.