I,ve set NLS_LANG = slovenian_slovenia.EE8ISO8859P2 and it is working!
There is no sign of "quoted string not properly terminated" error.
But now I have the other problem. My nacional charachters requires two places in a string. So if field's length is 10 and I insert string which containts 5 our charachters plus one more that I get message "inserted value too large for column"
What I would like to kwow is that normal. Becouse if that is normal I will just increase lenghts of varchar2 fields in database.