If I recall correctly, I think that on the second screen of the upload process (under the actual image) there is a check box to delete the image from the queue. So if you try to upload again, you should see the new upload and the one you want to delete both and can delete the other one.
Thanks Candy! I read your directions then read everything on the 1st upload screen. Got distracted and forgot to read the second upload screen. lol It let me upload anyway so I'll just have to check the directions next time.