Before I forget, here's a link to the tutorials, they will definitely explain this better than I can:
http://www.auctiva.com/help/tutorials.aspx#Toggle
But here's what I do..
Upload all pics
> Go to One Page Lister, fill in description, etc.
> Click on Select Image box
>>Do not click on Uploader link. Pics should be right there and visible, if not on the first page then on page 2 or 3 or 4 etc. If I still can't find what I want I will use the folder dropdown box. Ckick on desired pics and click Done.
This is all it should take. If it still doesn't work for you, you may have to file a support request. But be sure to take the tutorials. They're extremely easy to understand and very clear in their instructions.