Matlab freezes after calling a figure function in Ubuntu 15.04

I just updated my Ubuntu from 12.04 version to 15.04 (clean update, i.e., I erased my old Ubuntu 12.04 and installed the new one). I have Matlab R2013a installed in it and it used to work really fine, but now, all of a sudden, it freezes every time I try to plot anything. For example:

x = linspace(0, 10, 100); y = x;
[x, y] = meshgrid(x, y);
zx = x.^2 + y;
zy = x.*y;
quiver(x, y, zx, zy)

It freezes in such a way that I don't have access to any function. I can't use Ctrl + Alt + F2 or Ctrl + Alt + Del. The only thing that works is Alt + SysReq + REISUB, which reboots my computer.

In order to execute Matlab I have to run the command as super user in the terminal:

sudo /usr/local/MATLAB/R2013a/bin/matlab

If I don't use sudo, I get the following error message:

What can I do to solve this problem?

Thanks in advance,