If you’ve been editing an office file (Excel/Word etc) in Sharepoint when the application crashed – you’ll have found that when you try to re-open the file, it appears to be locked?
When you open a file in Sharepoint it’s automatically locked for 10 min. When you close the application – the file gets unlocked, however if the app crashes – the file remains locked!
The solution – wait 10 min 🙂
Here’s the official MS description: