When you change the language to "Bulgarian" there are two major problems:
1. There is no text on the "Send" button when composing a message and the button does not work. The text on the button is supposed to be "Изпрати".
2. When you receive an e-mail with no subject, there is no link to click on to read it. In English it shows "(no subject)", but in Bulgarian there's nothing. The text is supposed to be "(няма заглавие)"
I hope that you can fix that soon, because the webmail is useless in Bulgarian language that way.
I am using the latest squirrelmail - 1.4.22