Since I upgraded to Ubuntu 16.04 (actually a clean install) the virtual consoles sometimes appear black when I switch to them.
They still work, as I can type commands and things still happen (like if I type
espeak "hello world" my computer will say "hello world", or if I type
touch testfile I'll get a file named testfile in my home directory), but I cannot see anything on them.
Afterwards, if I switch back to my graphical desktop, the font rendering is sometimes all messed up and most of the characters (in any application) display as blank spaces or maybe a random dot or two. This doesn't always happen, even if the console was black.
Other times the consoles are fine and nothing is wrong with them. This seems to be more likely to happen if my system has been booted for longer or if I have already used the virtual consoles, but sometimes they're black when I switch to them for the first time a few minutes after booting.