The file manager on the Archos does a Microsoft and
doesn't display the file's extension in the list. Only when you rename the file doesn't it show you the
whole file name.
I copied over what I thought were the .epub files from my Opus. What I actually copied over were the .epub.dat files.
Which, of course, show up in the file list as .epub (since the .dat part is hidden).
So that's why the import didn't work. There really weren't any epub books in the directory. Once I copied over the
actual eBooks, the import went fine for Aldiko. I haven't done FBReader yet. The one file that I did for FBReader didn't show up.
Since what I wanted to do was test out eBook reading on the Archos 5 Android, having Aldiko working will satisfy my needs.