I had the same problem, since no one reported the problem, I thought it was only me
I solved it by running the DEV_server in administrator mode
If that doesn't solve the problem, switch to sqllite3, its much faster and it works on admin mode (doesn't work for non-admin)
Strange thing is that, when there is no DB file, without admin mode, it creates the DB file, but just can't modify it, on admin mode everything is great