I have ubun 17.1 and mint 18.3 dual boot.
I slightly prefer Mint over Ubuntu even though the "mint*" tools - which seem to be the main difference - are pretty primitive. This Mint forum is a lot better than the Ubuntu forum.
Ubuntu did the "spectre/meltdown" hack/fix better than Mint: in Mint I can't install any nvidia drivers after doing the (kernel) fixes, in Ubuntu no problems.
Mint 18.3 Xfce/fluxbox/pulse-less
Please edit your original post title to include [SOLVED] if/when it is solved!
Your data and OS are backed up....right?