I faced a similar problem(1. fonts of tab's title were blurred; 2.freezing when clicking global options) after installing texlive2015 in ubuntu 14.04. In order to access texlive fonts according to the link, I used these 2 commands in shell (Rstudio is normal before these operation):
$ cd /etc/fonts/conf.d $ sudo ln -s /usr/local/texlive/2015/texmf-dist/tex/latex/ctex/fontset/ctex-xecjk-winfonts 09-texlive.conf
After tring so many methods but invalid, Occasionally, I remove the file '09-texlive.conf', and refreshed:
$ sudo rm /etc/fonts/conf.d/09-texlive.conf $ sudo fc-cache -fsv
It back! I'm not sure why, but I hope it could give some hint for anyone encounter such dilemma. :D