I'm back on! It looks like it was a bad kernal update. 3.5.0-25 killed the box. 3.5.0-17 let me delete and reinstall it. Now back on the modern kernal and all's well.
i5 4440 3.1Ghz, Asus H87M-E motherboard, 8GB DDR3, 2GB DDR5 nVidia card, 2x500GB Seagate hd, Coolermaster 750W PSU running Mint 17.1 MATE and Win7
HP mini, 1.66 Ghz Intel atom processor, 2 GB DDR3, 320 GB hd, Mint 17 MATE