There is a bug(#407356) in XULRunner on Linux with non English keyboard layouts which breaks keyboard shortcuts like CTRL + C, CTRL + V, CTRL + T which effectively complicates life.

If you run in to the same issue as well you’ll be happy to find out that I have implemented Keyzilla extension, which works with Firefox, Thunderbird, Songbird and Komodo Edit. Hope Mozilla will fix this bug soon & will this extension useless, but till then my extension will help you out!