I am running 14.04 LTS, Unity, on an HP Pavillion 15, 4GBRAM, 750 GB hdd, I-5 machine, with AMD 8600M graphics card built in. I have disabled the dash and all Ubuntu spyware. I have been faithfully loading all updates as they appear. This morning it asked for a 94 MB update (bringing kernel to .27, I think. Now, I can boot, get to login screen, but it freezes after that. Keyboard doesn't work at that point, but mouse does. I booted into recovery mode, tried to run in generic graphics mode, -- system again froze. I also pressed [esc] during boot, but saw nothing strange; then text disappeared and was replaced by login screen. I am not a hobbyist; this is a production machine and I have a lot of work to do today. Having a standard software update render my machine completely useless... sigh. Perhaps the simplest thing to do would be to revert to the previous configuration. How do I do that? I can boot into recovery mode. But I have no idea how to proceed. TIA for all help. -Harry