There are bug reports involving the sp5100 module (for example https://bugs.launchpad.net/ubuntu/+s...x/+bug/1055096), and some people reported that blacklisting that module solved their problems.
Get to a terminal window: try ctrl+alt+F2 from your black screen & see if that gets you to a command line prompt. If so, login there. If that doesn't work reboot and select recovery mode from the grub menu and then choose "drop to root shell".
Run this command:
(In a root shell you can omit the word sudo.)
printf "blacklist sp5100_tco" | sudo tee /etc/modprobe.d/blacklist-sp5100.conf
That will create a file /etc/modprobe.d/blacklist-sp5100.conf containing the line blacklist sp5100_tco which should prevent the sp5100 module from loading. Reboot & see if that helps. If not, you can easily delete that file.