File Error: The specified file is locked.

Have you tried doing a Save as... with a different name?

This error is usually a result of not having proper write permissions with the original file. I've encountered this error many times on our Xsan. Where are you saving your project files to?

There is an option for disabling permissions on external drives, you should verify that this option is turned on.

From the desktop, click once on your external hard drive's icon, then press Command I to open the Get Info window. Look at the bottom of this window and look for the following checkbox: "Ignore ownership on this volume".

http://www.grabup.com/uploads/17b96753d93a38534b078376cfc1f7ca.png

if you copied the project from another computer or hard drive, it's possible the project file could retain ownership from the original computer.