SOLVED: Can't log on to the web UI

I am having an issue with my OMV. I have had it up and running happily for some time now.
But recently I have not been able to log on to the web UI. I don't get the 'incorrect password' error message, the screen refreshes and displays the log on prompt again.
All of my other services are working, and I can even SSH into it.

Does anyone have any idea what I may have done, or how to fix it?

Thanks

That was the problem exactly, Thanks.
I had been moving a few directories around through the terminal and somehow replicated one of them to /.