Tamil typing renders incomplete letters, but displays complete letters after pressing enter key

Libre office writer version,
OS : ubuntu Gnome 14.04 LTS (upto date),
Tamil Phonetic keyboard m17n used

while typing documents in tamil in libre office writer, the letters do appear on the display but often rendered incomplete especially in the lower part of each letter. All of these incompleteness vanishes the moment I press enter key and go to the next line. I do use LOHIT TAMIL font (if it may help) while typing. Please do suggest a solution to this issue.