I run my own server so I don’t know if this is possible and would really like to know. My documentroot has a log directory where errors are recorded and I had problems uploading early in my configuration that lead me to wonder about things like permissions.
It turned out to be an Apache error or Mod_Security more exactly that was liniting what I could do. If this just happened without any changes then maybe you host has made a security change that caused it.
Have you looked at your error log to see what is causing the problem?
