When you log into the GUI (with kernel version 3.5), type ctrl+alt+T to open a terminal, then run:
if the result of this command contains the
3.8.something numbering, edit your question to include its output.
sudo apt-get remove linux-image-3.8.* linux-headers-3.8.*
sudo apt-get autoremove
Restart your computer. Edit your question if you cannot log into the GUI or have found any other problem with this procedure. Otherwise, open a terminal again and run
sudo apt-get update && sudo apt-get dist-upgrade
then restart again and see if it worked.