using Pixelmator 2.1.2 and iPhoto 9.4.1 on a 10.8.2 OS X system I am unable to open any photo from my iPhoto library. I get a "Could not open" message.
I created a new iPhoto library just for this test. The jpg files themselv sit on an external drive, using the "Reveal in Finder" command in iPhoto shows that they are correctly referenced.
Any ideas on what the problem might be?