iPhoto library won't load thumbnails or pics

A couple of months back, I noticed that some thumbnails in my iPhoto library were not being loaded (maybe 10% of folders), and a number of photo's inside the folder were blank, and would also not load. The folder thumbnails would flicker on and off when scrolling down the folders, and the folders themselves show the 'reflection' of the folder pic in front of it, but not on the actual, folder.

I then noticed that some folders had totally disappeared, so I restored from my Time Machine from a couple of months previous. Missing folders re-appeared, but I still had blank thumbnails, and pics unable to open. I tried the 4 iPhoto repair options, but it made no difference.

I then restored from an even older Time Machine backup, but now, most of my thumbnail pics are missing (about 90%), and I can't open most of my photos. I don't understand how this is happening, as when the backup was made, the iPhoto library was fine.

I'm now beginning to think that my hard drive on my Mac may be corrupt, and I'm restoring to a faulty drive. Can anyone help?

I'm on OSX 10.6 (I think), and it may be worth noting that I tried updating the OS 2 months ago, but it crashed my Mac, and I had to restore.

Thanks

Lee