Since the upgrade from Ubuntu 13.10 to 14.04, I have problems with my screens.

My video card is a Radeon HD 7870, it uses the fglrx-updates driver. My main screen is a 24" with a resolution of 1920×1200 and the video card is also connected to a 50" 1080p TV. I want to use only the 24" screen at boot, I use xrandr to display the image on both screens when needed.

After the upgrade, Ubuntu displayed the desktop on both screens in extended desktop mode. The size of all the text was bigger, it was ugly.

I searched a solution to this problem and found someone who suggested to use amdcccle in order to define the screen settings. So I configured the 24" as the only screen in amdcccle and rebooted. Now the problem is still present, after every reboot the desktop is displayed in extended desktop mode on both screens, but the text is not zoomed like before using amdcccle.

The problem is the same if I use the screen configuration tool integrated in Gnome Shell.

I can use xrandr at the start of my session to force the resolution but I'm looking for a direct solution.

Update

As suggested in the comments I switched to the open-source drivers. After a reboot the dual-screen is still activated:

Once I deactivate the TV the display is correct except the window titles which are big:

Update 2

This behaviour is random, sometimes the text is not zoomed.