The command uname -r gives 3.5.0-17-generic, but when I checked in synaptics the kernel 3.5.0-43 is installed, but it seems the system uses the old kernel instead.
How can I make it use the new kernel?
SnapOverflow
Have you restarted since installing the new kernel? A kernel cannot be fully updated until the computer is restarted. If this does not work, try reinstalling 3.5.0-43. You should also try Software Updater to get new versions as none of those are the newest version.