What I basically meant with "numerous things" was the following step-by-step instructions I found here.
I translated them into english:
1) plug in iphone (quit iphoto in case it starts) and select "no events" in the photo-sync-section, then sync.
2) unplug iphone, quit itunes.
3) start iphoto while pressing the "alt"-key. create a new temp iphoto library (it doesn't matter where).
4) create at least one event by adding some (at least one) random photo(s) so that there is an event. after getting at least one event, quit iphoto.
5) open itunes, plug in iphone and wait until the automatic sync is done. then select just the recently created temp-event in your photo-sync-section. then sync. after syncing, unplug iphone, quit itunes.
6) now we want to use the original iphoto-library again. so start iphoto again while pressing the "alt"-key, select your standard iphoto library. after that, quit iphoto.
7) open itunes, plug in iphone and wait until the automatic sync is done. now you should see all the events correctly in the photo-sync-section and you can sync happily again.
And yeah, all those steps didn't work for me without the last step, which is:
8) close itunes. open iphoto (standard library), delete your iphoto-trash. quit iphoto again. open itunes (with your already plugged in iphone) and be surprised that you can see all the events correctly displayed.
As always: Hope that works for you too!