This may sound silly but another thing to look at is Apache is case sensitive, but PWS is not. Migrating from PWS to a normal web server means if you have things like photo.JPG (the way photoshop likes to name things) or Photo.jpg, a hit on photo.jpg will suffice on the former, but not the latter.
What is readdir coming back with? Does the NIX / Win32 output match? By "doesn't display the images" do you mean that they show up as broken?
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jb