Host not working on 10.10.3

[RemMac]

I've installed the latest host on a Mac mini with 10.10.3. This machine doesn't have a monitor attached. I've disabled screen lock on System Preferences but still everytime I connect it goes to the login window.

When trying to log in I get:
"The screen cannot be captured at the moment. This is probably due to fast user switching or a disconnected/minimized Remote Desktop session."

Sometimes it just hangs without the error message. Closing and trying again doesn't help. Only a complete reboot helps but a while later it stops working again.