Problem with retrieving photos from Time Machine.

A few days ago I reinstalled OS X. Before that I backed up the entire drive with Time Machine to an external hard drive. However, when I copied my files back to the MacBook, everything looks fine except iPhoto.

Here is my problem: I have one backup from February, one from May and I did one just before the reinstallation in July. In the one from February my iPhoto library is 49 Gb. But in both the May and July backup the iPhoto library is also 49 Gb and they both say last changed in February, which isn't right. So all my photos after February is missing.

Now, the strange thing is that when I plug in my backup drive and start Time Machine and look at the iPhoto library in the different backups they show the correct size - May is 55 Gb and July is 61 Gb - but only for a few seconds! Then it changes to 49 Gb. The last changed date is still Februrary all the time, though. So something is there, because it shows the right file size, if only for a few seconds. I checked the backup drive with the disk utility and it seemed fine.

Any thoughts on how to retrieve my photos?