Hi hippophile1,
Thanks for posting about this behavior here. We were seeing some reports similar to yours around the time you started this thread and it appears something was amiss on eBay's end that was causing them to drop Auctiva hosted (and perhaps other externally hosted) images that were submitted as the header/gallery image.
We stopped receiving these reports fairly quickly after we first became of the issue and I'm under the impression that eBay's technical team was able to resolve whatever problem was causing this to happen.
In any event, if you are still encountering this behavior, please contact our customer support team by mousing over the "Help" tab within your account and selecting the "File Support Case" option.
-Mike