I upgraded to iPhoto 11 and didn't experience any problems with loss of photos. I cannot, however, access the preferences. Clicking on preferences or using the keyboard shortcut (cmd - ,) does nothing. I've tried deleting the com.apple.iphoto.plist file and even reinstalling iPhoto to no avail.
In console.app when attempting to open preferences I get the following error:
iPhoto11659 *** -NSPlaceholderString initWithString:: nil argument
In console.app when attempting to open preferences I get the following error:
iPhoto11659 *** -NSPlaceholderString initWithString:: nil argument