From the beginning I used editor.ImageGalleryPath = "/uploads" and only tried the full URL when that didn't work. Also, the uploads directory has been permissioned for write access by IUSR as I mentioned in my initial post. I have tried putting the uploads directory in the wwwroot and in the same directory as enableall.asp but to no avail. The upload frame in the dialog box is empty either way, so I cannot upload files to the image gallery, which is probably why I can't see anything there.
One thing I have noticed, which may be unrelated, but when I click on the "up arrow" icon in the "Insert/Edit Image" dialog box I get an error on line 187 of insert_image.asp, "object doesn't support this property or method".
Everything else works fine--would love to get this figured out.