Lost menu for apps on Ubuntu

I have been using Ubuntu and Open Office without any problems for last two years. Suddenly, and I have no idea why, I have lost menu for apps, file manager etc. I can still run word, spreadsheet for Open Office but I must open an existing document or spreadsheet to start a new one. I cannot however do any operations with files like trasnsfer to/from USB or delete files as there is no menu whatsoever. I am IT illiterate. Please help!