iPhoto open in (null)

Is there anyone out there who can

1. Tell me what this stupid message means?

2. Suggest what to do next after I have unsucessfully tried deleting iPhotolock.data and lockfile.pid?

I have iPhoto '11 version 9.3.1 (652.4), downloaded and installed today. It will open one of my iPhoto libraries perfectly but when I try and open the other using alt & selecting it it won't open. I get messages which lead to repairing permissions but it is unable to do this and the end result is the "open in (null) message.

I would be very grateful for any help with this, please.