from you XI homepage, select the option ADMINISTRATION.
In the page that opens, there will something called LOCK OVERVIEW, click on it and just UNLOCK your locked object by
selecting Remove selected locks.
P.s You will have to make sure that you have the Administration access on your XI server.
pls try this option and see whether it works for you. I faced similar problem in the past and it got resolved.
Access your XI server through Interner Explorer. Go to 'Administration' link on main page. On the next page in 'Repository' tab you will get the option of 'Lock Overview' under 'Administration of Locks'. You can unlock the locked objects from here.