I'm sorry my knowledge cant help you much more but, this method has not failed for me
first you'll need to uninstall fglrx by typing into the terminal
./usr/share/ati/fglrx-uninstall.sh.then you should reboot.secondly get your drivers from here remembering you want the mobile HD 5 series for 32 (x86) or 64 bit in this case.
when they finish downloading , you'll usually need to add execute permissions then execute the script.
when it loads i choose Install over xorg (usually 6.8) or later i find problems occur when using the build package option. it should finish with no problems then you should check the log the directory will be given to you when the installer ends (even if it fails)
if everything is ok then run sudo aticonfig --initial
i suspect we can further pinpoint the problem with parts of the install log, which now come to think of it i think is located at
even if it fails you'll need to reboot before you can remove the drivers.if you don't intend to do GPU intensive tasks however the open source drivers should suffice and they will come in system updates from update manager