Comment 38 for bug 1578317

I clean installed Ubuntu 16.04 on a Dell Optiplex 390 and experience the same lack of mouse function after successful login. I attempted the workaround listed at the top of page but received the following error: "modprobe: ERROR: could not insert 'usbhid': operation not permitted.
  I then noticed my keyboard, which had previously worked normally, had stopped working. I unplugged both my keyboard and my mouse and reconnected both in turn and now my mouse and keyboard both work - even after log out and successful login. I am not a Dev, just reporting what I've noticed and wondering when a permanent fix will be available.