The number one reason images fail to upload is while they are going up if you chose any other tab, like design it will make the upload quit with an error notice sometimes, but usually no notice. It just isn't there. So when uploading don't choose any other options. Slow internet speed causes failure to upload. We have a lot of that going on right now. Upload one at a time, don't drag too many into the box, makes things too slow, one may load the others fail.