Aperture "no image found" problem

[davidinva]

Apparently posted this in the wrong forum at first (digital photography). I have Aperture 3.1.3 (updated recently). I don't use the program much and haven't for about a month. After updating, I opened it and have a library displayed in the browser. The library resides on an external drive along with 5 or 6 other ones (arranged by year). I can look at my photos but can't edit them because of the "no image found" message. I am having no luck in reconnecting masters and also can't see the other libraries in the list of Aperture Libraries. I copied the 2011 library to my hard disk, but still can't reconnect masters. Help please. I have few edited photos, so should I just start over? Thanks