The releases notes are short for this update to iPhoto ’11:

This update fixes a problem that could cause some events merged in iPhoto to be split back into multiple events on iOS devices after being synced.

We have heard a few reports of this issue, but it didn’t seem to be affecting every iPhoto and iOS user. As usual, head to Software Update, the Mac App Store or Apple’s website for the update.

Let us know in the comments if Apple has straightened things out with this update.