If you have Aperture 3.3 or later and iPhoto 9.3 or later you can merge libraries with Aperture.
Otherwise the only way to merge Libraries is with the paid ($20) version of iPhoto Library Manager
The messages you are getting sound more like an issue with your Library.
There are 9 different versions of iPhoto and they run on 9 different versions of the Operating System. The tricks and tips for dealing with issues vary depending on the version of iPhoto and the version of the OS. So to get help you need to give as much information as you can. Include things like:
- What version of iPhoto.
- What version of the Operating System.
- Details. As full a description of the problem as you can. For example, if you have a problem with exporting, then explain by describing how you are trying to export, and so on.
- History: Is this going on long? Has anything been installed or deleted? - Are there error messages?
- What steps have you tried already to solve the issue.
- Anything unusual about your set up? Or how you use iPhoto?
Anything else you can think of that might help someone understand the problem you have.