iphoto froze when downloading update, have lost all pictures. Can I retrieve?

I'm being told to re-download iphoto from ilife - but won't this mean I have lost all my valued pictures? Why does downloading new updates cause so many problems? When I tried to update my iphone to IoS5 it froze the phone and I lost all my contacts, messages and info. Unbelievably I then couldn't retrieve from my backup as it demanded a password and, despite hundreds of attempts to input it, I was told by Apple tech support that there are big problems with iphone backup passwords. They admitted that they can't help with passwords as the Mac and iphone generate new passwords every time you charge your phone on another machine that not your own. HEEEELP.