Could not save file

[caligula]

What does this annoying message mean and why does it seem to pop up arbitrarily for no reason? "Could not save the file because the file was left open or is in use." Is photoshop busy doing something underneath the hood? I am then forced to save the image as a copy and end up cluttering up my hard-drive with multiple copies of the same image or eventually the message goes away and I can then save my file without creating a duplicate.

[Old Geezer]

Are you saving over your original file ? Not a good idea, if it corrupts while you are saving, you are stuffed. Save it as a copy until you are certain it is what you want then wipe it from your hard drive.

[caligula]

OK, but why does the message happen?

[Old Geezer]

To stop you loosing or overwriting a file by mistake, or it cant do it because it is not properly prepared, so just ignore it as it stops you doing something you are not supposed to........;)