Upgraded to Ubuntu 15.10 the other day and the new kernel 4.2.0-21 would just freeze the system either with a black screen or a message saying kernel panic and the caps lock light would blink. As a work around I held down shift when Ubuntu started to boot and choose an older kernel.
What worked was to select wily-proposed in software updates as shown here:
Then in a terminal (ctrl-alt-t):
sudo apt-get update sudo apt-get upgrade
So far all the problems, freezing and errors I was having with updates and programs crashing are gone. This seems like a pain for such a big update but is working well for me!
I posted this originally on Ask Ubuntu here Kernel panic after upgrade to Ubuntu 15.10
Ubuntu is such a good alternative to Windows and I feel everyone should try it out… Ubuntu home page