Thank you for looking into this. To clarify, I had attempted an in-place update from 15.10 to 16.04. The update experienced some errors along the way, but on reboot I was nonetheless in 16.04. But now I got a series of error reports upon login (it never showed me the details). In an attempt to resolve the problem, I attempted an OS reinstall, booting from the LiveDVD for 16.04. In the process, I selected the option to install 3rd-party drivers, and was prompted that I would need to disable EFI (I have no idea whether EFI was previously active). I approved it, then at the end of the installation was informed that Grub had failed to install; the dialog that was supposed to then take me to a bug reporting screen was then stuck, and couldn't be dismissed - I had to do a hard reset. The startup after this is when I encountered the exception and used the error reporting tool to open this ticket. Unfortunately, I won't be able to provide you with any more details about my system configuration, because I then re-ran the LiveDVD installer, this time blowing away my system partition & installing clean (I had /home mapped to a different physical volume, which proved very convenient in this case). I did not select the option to install 3rd-party drivers, and my system now boots and runs cleanly (I just have to re-install all my optional software :( ). On Mon, May 16, 2016 at 12:50 PM, Steve Langasek <