For some reason my third generation Dell Sputnik (aka Dell XPS13 with Ubuntu pre-installed) sometimes has a frozen or broken mouse / cursor after I suspend or sleep my laptop. You can easily get it working again (this is not a permanent fix) by switching to a different TTY and then back to the TTY that holds the x-server GUI.
- ctrl+alt+F6 to switch to TTY6 (this will give you a terminal)
- Do nothing in the terminal
- ctrl-alt+F7 to switch back to the TTY7 which is the Ubuntu x-server
- Voila... your mouse should be working again.
If anyone has a permanent fix, please let me know.