When I am asking about the error, I meant to ask what the actual error message was. As for the method, you list several in your original post. Are you saying that you retried all of them and still none of them work?
Regarding Special:MultiUpload, I sounds like it might be some behind-the-scenes limit you were hitting. As for the script, did you try to upload them all at once? The script limits you based on your user rights.