Log-in prompt often on wrong monitor in dual monitor setup

I often get the log-in prompt on the wrong monitor (VGA-0) in a dual monitor setup with a laptop panel (LVDS) and an external LCD TV (VGA-0). So I have a situation with a black screen on LVDS (i see the mouse cursor in the intersection between the monitors on the left edge of LVDS) and the log-in prompt displayed on VGA-0 which is also black (turned off). Is this related to lightdm and why not always use the primary monitor (LVDS) for login-prompt?

xrandr:

Screen 0: minimum 320 x 200, current 3320 x 1080, maximum 8192 x 8192
VGA-0 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 886mm x 498mm
LVDS connected primary 1400x1050+1920+0 (normal left inverted right x axis y axis) 287mm x 215mm
DVI-0 disconnected (normal left inverted right x axis y axis)

lwhw:

 *-display
                description: VGA compatible controller
                product: RV515/M54 [Mobility Radeon X1400]
                vendor: Advanced Micro Devices, Inc. [AMD/ATI]

lightdm --version : lightdm version 1.8.5
uname -r : 3.11.0-19-generic
ubuntu: 13.10

.config/monitors.xml:

<monitors version="1">
  <configuration>
      <clone>no</clone>
      <output name="VGA-0">
          <vendor>SAM</vendor>
          <product>0x04fa</product>
          <serial>0x00000000</serial>
          <width>1920</width>
          <height>1080</height>
          <rate>60</rate>
          <x>0</x>
          <y>0</y>
          <rotation>normal</rotation>
          <reflect_x>no</reflect_x>
          <reflect_y>no</reflect_y>
          <primary>no</primary>
      </output>
      <output name="LVDS">
          <vendor>LEN</vendor>
          <product>0x4022</product>
          <serial>0x00000000</serial>
          <width>1400</width>
          <height>1050</height>
          <rate>60</rate>
          <x>1920</x>
          <y>0</y>
          <rotation>normal</rotation>
          <reflect_x>no</reflect_x>
          <reflect_y>no</reflect_y>
          <primary>yes</primary>
      </output>
      <output name="DVI-0">
      </output>
  </configuration>
</monitors>