when i try to join any online multiplayer [including my own server] it seems like it is going to work but then it gives me the following message:
"
Failed to connect ot the server
Internal exception: java.lang.NullPointerException
"
followed by a button that says "Back to server list"

I expected it to let me into a public server [like mineplex].
what actually happened was that i got the above message.
steps to reproduce
open minecraft on desktop
launch version 1.11.2 or any version for that matter /vanilla
select multiplayer session
click on mineplex
click join server
error message occurs

tried with minecraft versions 1.8.3 and 1.11.2 and got the same results

windows 7 64bit operating system
java 1.8.0_25 64 bit
cpu: 4x amd phenom II x4 955 processor
display: 1920x1028 nvidia
geforce gtx 550 ti/pci/sse2
4.5.0 nvidia 347.52