Amnesia: "Failed to start game (app already running)"

[ejpwood]

Hi, I got amnesia as a birthday present. It ran fine for a week or so, then it stopped opening and displayed the message above. What I've tried so far:

- Closing steam in task manager. It got further then, but still stopped on "Error code 80".
- Deleting everything in steam folder except steam.exe and steamapps folder. Same result.
- Unchecking all compatibility options
- Creating a new steam profile; the launch screen then said we had to buy the game (didn't recognise I already had it)

I got these ideas from various support and discussion pages. I can't use the game - can anyone help?

Cheers

Ed