I had a similar problem under Lion with iPhoto '11 version 9.3.1 (Build 652.3). In my case I couldn't see the Last 12 Months of photos after I synced the iPhoto Library to my iPhone. I decided not to leave it that way and so I unchecked they iPhoto Sync option in iTunes for my iPhone and removed the synced items from my phone when prompted. Then when I looked at "Last 12 Months" in iPhoto (on my iMac) it showed stuff more than a year old and not the most current photos in my library. Strange... Not sure what happened but the way I fixed it was to go to iPhoto Preferences, and under General tab, Sources, I changed "Show last" checked item from 12 months to 10 months, and that seemed to fix it (it correctly showed the last 10 months of photos). Then I changed it back again to 12 months and it showed that correctly too. So, somehow something got messed up but changing the number of months it should show seemed to reset it and fix it. Not sure if this will help you in 10.6.8 with the slightly older iPhoto '11 but it might...
Force quit out of iPhoto and do the following: make a temporary, backup copy (select the library and type Command+D) and apply the two fixes below in order as needed:
Launch iPhoto with the Command+Option keys held down and rebuild the library.
Select the options identified in the screenshot.
Using iPhoto Library Manager to Rebuild Your iPhoto Library
- Download iPhoto Library Manager and launch.
- Click on the Add Library button, navigate to your Home/Pictures folder and select your iPhoto Library folder.
- Now that the library is listed in the left hand pane of iPLM, click on your library and go to the File ➙ Rebuild Library menu option
- In the next window name the new library and select the location you want it to be placed.
- Click on the Create button.
Note: This creates a new library based on the LIbraryData.xml file in the library and will recover Events, Albums, keywords, titles and comments but not books, calendars or slideshows. The original library will be left untouched for further attempts at fixing the problem or in case the rebuilt library is not satisfactory.