Binder is frozen - cannot switch between text docs

Good morning,
I’m working on windows 7, 64 bit, with the latest version of Scrivener,
I’ve never had a bug with Scrivener for Windows before.
This bug ONLY affects a SINGLE project of mine.
All my other projects are still working fine.
In this single project, it is impossible to switch between documents. One document alone remains on my screen no matter which doc titles I click on in the binder.
I have checked to make sure the padlock icon in the bottom right hand corner is unlocked in case I inadvertently locked the editor. All is well on that score.
The project still compiles perfectly well. In fact it does everything else with no problem. Only that, in Scrivener I cannot access any of my project docs, except one.
How did this happen? All I know is that one moment it was working perfectly and the next it was not. Apologies for not being able to describe a sequence of events leading up to the problem.
Any help gratefully appreciated.
Thanks in advance.

PS I tried uninstalling and re installing Scrivener but the problem remains.

Have you tried creating a new project and importing the documents from the frozen project? You could import one by one and test it to see if a certain document is causing the hangup.

The lock icon refers to the inspector, so it won’t tell you whether the editor is locked. For that, take a look at the editor header bar, where the document title is: if it’s pink, it’s locked. You can disable the lock by deselecting View > Editor > Lock in Place or deselecting Lock in Place from the icon menu in the editor header.

Thank you Sanguinius and Mimetic for your replies.
Mimetic, a thousand thanks - your suggestion worked. Blessings upon you, my life is saved.