I am having the same issue....it is not letting me choose photos. Listings I do from eBay are effortless and easy, Auctiva listings have been getting very troublesome.
Between slow processing of listings, recurring uploading issues, mysterious changing fonts, disappearing/reappearing images, item specific bugs, and the fact that eBay lets you upload many photos for free now.....I am beginning to wonder why I use Auctiva.