I am still using 14.04 (which still seems to be maintained, to my surprise).
Last week, it upgraded my kernel to Linux 3.13.0-149-generic. Since then I have the following problem:
I normally Suspend when not using the machine, with a request to de-suspend at 0400 each morning to do various housekeeping tasks. Since that upgrade, the de-suspension fails with a message
general protection fault: 0000 [#1] SMP
followed usually by various tracebacks and attempts to fix, most of which has disappeared off the top of the screen before it can be read. The keyboard and mouse are then completely dead, so I have to reboot, after which it informs me there has been a System Failure and do I want to report it (which I do, though my modem does not show much activity to indicate any report is actually being sent).
My hardware is i386 32bit using a Gigabyte Motherboard.
Once rebooted, the system works fine, with no evidence if hardware failure.