Special characters stop working

Greetings,

I've been using pycharm without any issues on MacOSX for a few months. After formating my macbook and installing Ubuntu 14.04, I started to note that sometimes my special characters stop working on pycharm window, and to make it work again, I have to switch to any other window (terminal, firefox, gedit,...) and type a few special characters, then if I go back to pycharm, most of the times the issue seen to be gone. If not, them I repeat the process until the issue disappears.

My settings are:

Ubuntu (Unity) 14.04 64bits
Language: pt_BR
Keyboard: (Standard US, us - international configured)

the special characters that stops working are (at least the ones that I noticed): ' " ^ ~(and its combinations as í é ç ^ ~)


Please note that those characters are result of combination of keypress, even for single quote:

<space> + ' = '
<space> + " = "


Any ideas or suggestions?
Thank you!