I've installed Lubuntu 13.04 on my notebook. (It's the first time I use Lubuntu) I had graphical issue, apparently due to the graphic driver (ATI Radeon Xpress 1200)

I followed this procedure to correct my problem :

sudo add-apt-repository ppa:makson96
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install fglrx-legacy

My graphical issue has been corrected but now it shows a low resolution (1024*768) and I can't change it.

the xrandr result :

xrandr: failed to get size of gamma output default 
Screen 0: minimum 1024x768, current 1027x768, maximum 1024x768
default connected 1024x768+0+0 0mmx0mm
1024x768 0.0*

I've already read this topic but I don't really understand how things work there.

I'd really appreciate your help !

Many thanks !