I've been testing the limits of the new Ubuntu/Bash shell on Windows and after restarting my computer it mysteriously refused to launch. Running bash from the command line yielded the following message:

Error: 0x80070002  

After a few attempts at repair I resorted to re-installing by issueing the following commands from the command line:

lxrun /uninstall /full

lxrun /install  

This reset the environment and deleted everything I'd done, but seemed to be the only option.

Back to square one.