Minecraft with OpenJDK 7, I get "the trustAnchors parameter must be non-empty"

Actually, a better answer is to enter the following at the command prompt.

sudo update-ca-certificates -f

Open a terminal and fire this command:

sudo apt-get install --reinstall ca-certificates-java

And make sure that the time setting of your system is correct.

_Source

I quote:

Basically, Minecraft uses SSL to protect your login, but Java didn’t have the certificates needed to verify. The Minecraft launcher really should give a better error message, but this was really Ubuntu’s fault. You need the ca-certificates-java package installed, but on my Ubuntu install, it was broken. Try doing ls /etc/ssl/certs/java/cacerts. If it comes up missing, then you need copy it from a friend or a different Unix machine. You don’t want to copy security files from strangers…