Resuscitating this thread because I'm having the same problem, on Windows 7 x64, PM version 5 build 13915. Here's the exact error I'm getting:
I've been using PM to export metadata for hundreds of thousands of images, which are stored in hundreds of folders along with a few other files of different types (GPX and PDF, mainly). It's gone well except for a few folders, where I'm getting the above error. Is there a way to show the image index numbers so I can de-select the file that's causing this problem? When the export runs, I can see it stopping at the image above (#5385 in this case), but that number doesn't help if I can't see the image index numbers.