I'm on OS 10.6.7 using 4.6.7 public beta 5 and discovered that I can't see any images stored on my external hard drive connected to my network via Airport Extreme. The folders show up, but PM shows zero images inside any folders. No issues using the Finder to access the images.
Couldn't figure out what was going on, so I went back to 4.6.6 and that solved it. So it's no problem, I'll just continue with 4.6.6 for now, but though I should let you know.
Cheers.