No, the issue was a corrupted ICEauthority. It can happen on any version of Ubuntu, I am pretty sure.
Mentioning the age of the distro package was a free and unrelated extra, because calibre moves fast and many things have changed in the 2 years since Ubuntu last updated calibre on 14.x
That's why the distro version is officially unrecommended -- even 15.10 has v2.35.0 packaged 4 months ago, and currently 10 releases behind.
Don't worry, Xenial just updated from there to v2.45.0 about an hour ago. But that is their unstable development version.