Overview: A couple of days ago, I did a fresh install of Archlinux+XFCE4. I have a Radeon HD 4770 graphic card and I'm using the open source drivers. 
My main screen is connected via DVI-DVI. The screen I try to connect will be via HDMI-HDMI, although I tried VGA-VGA as well with the same result.


Steps to Reproduce: In Settings > Screen, the option to configure new screens when they are connected is marked. In fact, when I connect my second screen, a window pops up with four different options. No matter what I choose, my system gets frozen and I had to hard reboot.


Actual Results: The system gets completely frozen. 


Expected Results: The second screen should display the desktop.


Build Date & Hardware: Build 2015-05-01 on Archlinux 4.0.1

Additional info: display.xml file under .config/xfce4/xfconf/xfce-perchannel-xml/

<?xml version="1.0" encoding="UTF-8"?>

<channel name="displays" version="1.0">
  <property name="Default" type="empty">
    <property name="DVI-0" type="string" value="1. Ancor Communications Inc 22&quot;">
      <property name="Active" type="bool" value="true"/>
      <property name="Resolution" type="string" value="1920x1080"/>
      <property name="RefreshRate" type="double" value="60.000000"/>
      <property name="Rotation" type="int" value="0"/>
      <property name="Reflection" type="string" value="0"/>
      <property name="Primary" type="bool" value="false"/>
      <property name="Position" type="empty">
        <property name="X" type="int" value="0"/>
        <property name="Y" type="int" value="0"/>
      </property>
    </property>
    <property name="HDMI-0" type="string" value="1. Goldstar Company Ltd 22&quot;">
      <property name="Active" type="bool" value="true"/>
      <property name="Resolution" type="string" value="1920x1080"/>
      <property name="RefreshRate" type="double" value="60.000000"/>
      <property name="Rotation" type="int" value="0"/>
      <property name="Reflection" type="string" value="0"/>
      <property name="Primary" type="bool" value="false"/>
      <property name="Position" type="empty">
        <property name="X" type="int" value="1920"/>
        <property name="Y" type="int" value="0"/>
      </property>
    </property>
  </property>
  <property name="Notify" type="bool" value="false"/>
</channel>


No matter what I change in this file, my systems apparently accept those changes but after 4-5 seconds it gets frozen.