When you say, "work wasn't saved", do you mean you never saved that project or that you worked for a while without saving, but the project had previously been saved?
That is to say, is there a chance that you have an autosave of your file?
Also, what, exact, version of AE are you using? What OS? What happened when you got the error message? What were you doing when it happened?
Also, check out this thread: unbalanced unlock ( 7 :: 40 )
Are you still facing this problem? If not, let us know how you solved it. If so, please let us know so we can assist you further.