Hi
Make sure that you are trying to upload the actual images and not links to them stored in another folder.
Sometimes things in the Library are just a link to the actual file.
I would try is to make a folder named, "Photos for Ebay".
Copy the photos you want to upload to the new folder and try and upload them from there.
The other thing that comes into play is the file type.
Are you trying to upload files that are a different type, i.e. .tif, .png, etc.
You may be trying to upload a file that ebay doesn't recognise, make sure that the are in some common format like .jpg.
Mike