I have my computer set up with photo stream to automatically import photos into my library when using my Canon 60D & my iPhone however often they disappear from my library & even trying to import duplicates manually they also disappear?

I have my computer set up with photo stream to automatically import photos into my library both for my Canon 60D & my iPhone 3GS, however while at first they show up in my library after closing down my computer when I reopen it the photos will only show up in my photo stream that have come from my canon 60D & have disappeared from my library showing only a palm tree for the event with no photos in it & this is the case also if I have made an album using some of the photos. This also occasionally occurs with my iPhone 3GS although not as often. When I try to import the photos again manually it tells me that they are already in the library or if I try to share them it tells me to do so from my library, but of course they are no longer visible there or in the albums I made. On a very erratic schedule the box appears that there are library inconsistencies noted, but it is not a common occurrence. When inconsistencies are noted of course it fixes it, but otherwise even if I import duplicate files of the photos, they also disappear. Does anyone understand what is happening to my photo library?